Kinky heteros plus one? (9)
I believe the answer is:
threesome
'kinky heteros plus one?' is the definition.
I can't judge whether this definition defines the answer.
'kinky heteros plus one?' is the wordplay.
'kinky' indicates an anagram.
'plus' is a charade indicator (letters next to each other).
'one?' becomes 'me' (a setter might use 'one' to humourously mean 'me').
'heteros' anagrammed gives 'threeso'.
'threeso'+'me'='THREESOME'
(Other definitions for threesome that I've seen before include "Horse meet (anag.)" , "a crowd, perhaps" , "Triad" , "triplets, perhaps?" , "triangular event" .)