Castrate (6)
I believe the answer is:
neuter
'castrate' is the definition.
(I know that castrate can be written as neuter)
This is the entire clue.
(Other definitions for neuter that I've seen before include "De-sex" , "Tureen (anag.)" , "Make ineffective; gender" , "Retune (anag.)" , "Sexless" .)