Gender
'gender' is the definition.
(I have seen 'A gender ' mean 'male' so perhaps 'gender' could also mean 'male')
This is the entire clue.
(Other definitions for male that I've seen before include "As are drakes, bulls etc." , "Maldives capital; masculine" , "A gender" , "Lame sort of fellow" , "One cannot have babies" .)
(Other definitions for fluid that I've seen before include "Aqueous" , "Not solid" , "Liquid or gas" , "Flowing" .)