I have a shot at a villain (4)
I believe the answer is:
iago
'villain' is the definition.
(I've seen this in another clue)
'i have a shot at a' is the wordplay.
'have' means one lot of letters go next to another.
'a shot' becomes 'go' (both can mean an attempt).
'at' says to put letters next to each other (I've seen this in other clues).
'go' after 'a' is 'ago'.
'i'+'ago' is 'IAGO'.
(Other definitions for iago that I've seen before include "villain in play" , "Othello's treacherous counsellor" , "Othello's enemy" , "stage villain" , "Organ stop" .)