To stew (6)
I believe the answer is:
braise
'to stew' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for braise that I've seen before include "Stew in a closed pan" , "Cook slowly with little liquid in closed container" , "Fry then stew slowly" , "Fry then stew (meat)" , "13 across (anag)" .)