Tiny part from a male cat (4)
I believe the answer is:
atom
'tiny part' is the definition.
(I've seen this in another clue)
'a male cat' is the wordplay.
'male cat' becomes 'tom' (a male cat is called a tom).
'a'+'tom'='ATOM'
'from' acts as a link.
(Other definitions for atom that I've seen before include "A tiny powerful particle" , "Tiny particle, causes mighty explosion" , "type of bomb" , "Particle; molecule" , "An explosive particle as in bomb" .)