Alpha male finds grain (4)
I believe the answer is:
atom
'grain' is the definition.
(thesaurus)
'alpha male' is the wordplay.
'alpha' becomes 'a' (phonetic alphabet: alpha, bravo, charlie etc.).
'male' becomes 'tom' (I've seen this before).
'a'+'tom'='ATOM'
'finds' acts as a link.
(Other definitions for atom that I've seen before include "A tiny particle but a big bomb" , "Something very small perhaps" , "Small particle of matter" , "The tiniest particle" , "Tiny particle, causes mighty explosion" .)