Sexless tune composed with hesitation (6)
I believe the answer is:
neuter
'sexless' is the definition.
(I know that sexless can be written as neuter)
'tune composed with hesitation' is the wordplay.
'composed' indicates an anagram.
'with' is a charade indicator (letters next to each other).
'hesitation' becomes 'er' (sound made while hesitating - um, er).
'tune' anagrammed gives 'neut'.
'neut'+'er'='NEUTER'
(Other definitions for neuter that I've seen before include "Neither masculine nor feminine gender" , "Make ineffective; gender" , "Neither male nor female" , "De-sex" , "Neither m nor f" .)