Figure it's overheard (3)
I believe the answer is:
two
'figure' is the definition.
(two is a number)
'it's overheard' is the wordplay.
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'overheard' becomes 'wo' (I can't explain this - if you can you should believe this answer much more).
't'+'wo'='TWO'
Can you help me to learn more?
(Other definitions for two that I've seen before include "Old song 'Tea for . . .'" , "2" , "Prime number" , "Number of faces of the god Janus" , "Cardinal number" .)