Little bit from a male cat (4)
I believe the answer is:
atom
'little bit' is the definition.
(thesaurus)
'a male cat' is the wordplay.
'male cat' becomes 'tom' (I've seen this before).
'a'+'tom'='ATOM'
'from' acts as a link.
(Other definitions for atom that I've seen before include "An explosive particle as in bomb" , "Particle; molecule" , "A wee bit" , "Piece of matter in moat" , "A tiny particle of matter with a big bang" .)