Vegetable that's acceptable uncooked mostly (4)
I believe the answer is:
okra
'vegetable' is the definition.
(okra is a kind of vegetable)
'acceptable uncooked mostly' is the wordplay.
'acceptable' becomes 'ok'.
'uncooked' becomes 'raw' ('raw' can be similar in meaning to 'uncooked').
'mostly' means to remove the last letter.
'raw' with its final letter taken away is 'ra'.
'ok'+'ra'='OKRA'
'that's' acts as a link.
(Other definitions for okra that I've seen before include "Long green tropical vegetable" , "Green pods, in stews" , "Edible seed pods" , "Bhindi in Ind. cookery" , "vegetable soup ingredient" .)