"It's a female," you declared (3)
I believe the answer is:
ewe
'it's a female' is the definition.
(female sheep)
'you declared' is the wordplay.
'declared' shows a homophone (sound like).
'you' sounds like 'EWE'.
(Other definitions for ewe that I've seen before include "Lamb's dam" , "Ruminant" , "Language" , "The sort of beast" , "Female bleater" .)