Mousy little chap? (5)

I believe the answer is:

jerry

I'm a little stuck... Click here to teach me more about this clue!

This might be a double definition.

'mousy little' is the first definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

'chap?' is the second definition.

Can you help me to learn more?

(Other definitions for jerry that I've seen before include "- - Hall, model and actress" , "Tom and --, cartoon" , "Cartoon mouse" , "-- Lee Lewis" .)

I've seen this clue in the Evening Standard.

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