Cooks turning west start to simmer (5)
I believe the answer is:
stews
'cooks' is the definition.
(stewing is a kind of cooking)
'turning west start to simmer' is the wordplay.
'turning' indicates an anagram.
'start to' says to take the initial letters.
The initial letter of 'simmer' is 's'.
'west' anagrammed gives 'stew'.
'stew'+'s'='STEWS'
(Other definitions for stews that I've seen before include "Cooks slowly in liquid" , "Simmers" , "casseroles?" , "Swelters" , "Ragouts" .)