Kisser's role reversal (4)
I believe the answer is:
trap
'kisser's' is the definition.
(I've seen this in another clue)
'role reversal' is the wordplay.
'role' becomes 'part' (eg a part or role in a film).
'reversal' says the letters should be written in reverse.
'part' written backwards gives 'TRAP'.
(Other definitions for trap that I've seen before include "Light horse-drawn carriage" , "Part of a snare" , "corner" , "Golfing hazard" , "The Web" .)