Animal half strung up (3)
I believe the answer is:
gnu
'animal' is the definition.
(type of antelope)
'half strung up' is the wordplay.
'half' suggests halving the letters.
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'strung' cut in half is 'ung'.
'ung' written backwards gives 'GNU'.
(Other definitions for gnu that I've seen before include "hitherto unknown, we hear" , "Wildebeest" , "Large heavy antelope" , "Gun for a kind of deer" , "Literally wild beast" .)