Did my line manager try to embarrass me in front of others by purpose?

Alright, I suppose we all had to have this sort of thing explained to us once upon a time.

Quite how nasty it might have been probably depends on context, including whether or not they had been drinking during the meal. 

From what you've said, it sounds like an unwise attempt at https://en.m.wikipedia.org/wiki/Double_entendre during a mixed work gathering.

The manager made a comment which highlighted a double meaning from the older female. The underlying and probably wholly unintentional double meaning was that the older female was making a sexual advance towards you.

The evil stare was probably one or several of:

1. You know that's not what I meant
2. Don't be crude
3. Don't embarrass our junior colleague 
4. Oops, I didn't intend a double meaning, but now you've raised the possibility of doubt in people's minds. That potential doubt that I might have just attempted a sexual advance embarrasses me. 
5. Darn it, I've just lost this "round" of the who-can-twist-others'-comments-into-something-a-bit-naughty word game.

The laughter came from:

1. The older female making a probably innocent request that could be interpreted in a sexual way, thereby making her intent ambiguous. 
2. Your innocent offering of the requested items. This indicated innocence of the double meaning and implicitly innocence of sexual matters. 

In the UK, it is quite an old (and now out-dated) custom to poke fun at the innocence of junior colleagues when they enter the world of work for the first time. So for instance:

The new apprentice in a factory might have been sent down to the stores for a long stand. Upon arriving at the stores, the store clerk (who was of course in on the joke) would reply with a straight face, "A long stand you say? OK, just wait there, I'll be back soon", before disappearing into the stores.

After a quite considerable time, the store clerk would reappear, with the words, "Well? Did you enjoy your long stand?" before laughing and asking if there was anything else you actually needed...

How upset you get if you are on the receiving end of this sort of mucking about rather depends upon your social resilience, and how well you can control your own feelings of embarrassment when you realise that someone has been playing a trick on you. These customs developed because people who had been tricked remembered the joke and repeated it themselves on the next generation to enter the workforce. It was a way of escaping from the boredom of repetitive work, albeit at someone else's expense.

Most of the time, after a bit of joking about, things settle down, because there is real work to do, and most people have a conscience which stops things getting too nasty.

Very occasionally, however, a more malicious dynamic is created, and repeated victimisation takes place, perhaps because the group sense that the butt of the jokes is identifiably different in some way.

That's workplace bullying.

In the UK, it is quite an old (and now out-dated) custom to poke fun at the innocence of junior colleagues when they enter the world of work for the first time. So for instance:

The new apprentice in a factory might have been sent down to the stores for a long stand. Upon arriving at the stores, the store clerk (who was of course in on the joke) would reply with a straight face, "A long stand you say? OK, just wait there, I'll be back soon", before disappearing into the stores.

After a quite considerable time, the store clerk would reappear, with the words, "Well? Did you enjoy your long stand?" before laughing and asking if there was anything else you actually needed...

How upset you get if you are on the receiving end of this sort of mucking about rather depends upon your social resilience, and how well you can control your own feelings of embarrassment when you realise that someone has been playing a trick on you. These customs developed because people who had been tricked remembered the joke and repeated it themselves on the next generation to enter the workforce. It was a way of escaping from the boredom of repetitive work, albeit at someone else's expense.

Most of the time, after a bit of joking about, things settle down, because there is real work to do, and most people have a conscience which stops things getting too nasty.

Very occasionally, however, a more malicious dynamic is created, and repeated victimisation takes place, perhaps because the group sense that the butt of the jokes is identifiably different in some way.

That's workplace bullying.