It's gender (6)
I believe the answer is:
neuter
'it's gender' is the definition.
(neuter is a kind of gender)
This is all the clue.
(Other definitions for neuter that I've seen before include "Tureen (anag.)" , "Retune (anag.)" , "Neither male nor female" , "Neither masculine nor feminine gender" , "Castrate" .)