I also had to look up synecdoche. I did know about pars pro toto and totum* pro parte, which are apparently subclasses of synecdoches.
A metonymy (' "crown" in "lands belonging to the crown" ', says M-W) is quite close to a pars pro toto (a part for the whole: "England" for UK), but differs in that a pars pro toto uses a part of something to refer to the whole, whereas a metonymy uses one thing to refer to an associated thing (not necessarily part or whole of the same thing). Does that make sense?
But I don't know the answer to your question, OP. Does it have to be a figure of speech? I mean, can it not be literal?
*I'm quite sure I learned that as "totem", but googling it just now to find some good examples, it only turns up Indonesian and Dutch pages. Weird.