Females finally saw sign (5)
I believe the answer is:
women
'females' is the definition.
(woman is a kind of female)
'finally saw sign' is the wordplay.
'finally' suggests the final letters.
'sign' becomes 'omen' (omen is a kind of sign).
The last letter of 'saw' is 'w'.
'w'+'omen'='WOMEN'
(Other definitions for women that I've seen before include "half of our race" , "Adult human females" , "Ladies" .)