The most common and most likely answer to this crossword clue is the 6 letter word BRAISE
I've seen this crossword clue in The Daily Telegraph
B
R
A
I
S
E
More clues leading to the result BRAISE
- Cook hearing donkey calls
- Cook sounds like a donkey, you say?
- Cook is required in Scottish bank
- Two cups I notice shortly for stew
- Sea bream to stew slowly
- Head of bakery to promote cook
- It would make Angus flip to take in recipe by first-class cook
- Stew makes British grow
- Cook is breaking bank in Scotland
- Cook endless seabird stew
Buddy explains!

The straight part
We know that "Cook" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cook = braise.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does BRAISE mean?
BRAISE noun- A dish (usually meat) prepared by braising.
- A sauce used for braising.
- To cook in a small amount of liquid, in a covered pan, somewhere between steaming and boiling.
- A kind of small charcoal used for roasting ore.
- To join two metal pieces, without melting them, using heat and diffusion of a jointing alloy of capillary thickness.
- To burn or temper in fire.
- Pagellus bogaraveo, syn. Pagellus centrodontus (sea bream)