Antelope chews herb alright (6)
I believe the answer is:
rhebok
'antelope' is the definition.
(I've seen this before)
'chews herb alright' is the wordplay.
'chews' is an anagram indicator (I've seen 'chewed' mean this).
'alright' becomes 'OK' (synonyms).
'herb' is an anagram of 'rheb'.
'rheb'+'ok'='RHEBOK'
(Other definitions for rhebok that I've seen before include "South African antelope" , "South African game, perhaps" , "Small antelope; herb OK (anag.)" .)