Ape or nag, possibly (5)
I believe the answer is:
orang
'ape' is the definition.
(I know that orang is a type of great ape)
'or nag possibly' is the wordplay.
'possibly' is an anagram indicator.
'nag' is an anagram of 'ang'.
'or'+'ang'='ORANG'
(Other definitions for orang that I've seen before include "Primate" , "Forest-dweller with red hair" , "- - -utan" , "Large ape" , "Wild animal briefly appeared" .)