Thanks Jim - my point is that the definition is inaccurate and therefore potentially misleading. You wouldn't say 'there's one in Parliament' to define an MP for example.
It just seems a bit loose - there's one queen ant/Speaker, but many other ants/MPs. You might be hard pushed to find other examples in good quality crosswords.
I don't agree that this is a loose definition at all. An ant is "an insect that lives in a colony with many other ants, examples including the Amazon Ant." What's wrong with that? And less obvious than "Insect's endless indication of opposition"...