Promiscuous gents possibly used to get naked (5)
I believe the answer is:
loose
'promiscuous' is the definition.
(loose can mean promiscuous)
'gents possibly used to get naked' is the wordplay.
'gents possibly' becomes 'loo' (gents toilet).
'to get naked' indicates the central letters (the word is undressed of its external letters).
The central letters of 'used' are 'se'.
'loo'+'se'='LOOSE'
(Other definitions for loose that I've seen before include "Release" , "Showing fast behaviour" , "Unleash" , "Hanging" , "Not tightly fixed" .)