A gun and possibly a forename (7)
I believe the answer is:
brendan
'a forename' is the definition.
Both the answer and definition are singular nouns.
Perhaps you can see an association between them that I can't see?
'a gun and possibly' is the wordplay.
'a gun' becomes 'Bren' (Bren is an example).
'possibly' indicates an anagram.
'and' is an anagram of 'dan'.
'bren'+'dan'='BRENDAN'
Can you help me to learn more?
(Other definitions for brendan that I've seen before include "-- Behan, Irish author" , "Early Irish saint" , "- Behan, Irish dramatist" , "Chap" .)