Mush a chef originally left in box? (7)
I believe the answer is:
treacle
'mush' is the definition.
(I've seen this in another clue)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for treacle that I've seen before include "Saplike stuff" , "Sticky produce" , "Sticky fluid" , "Thick syrup from sugar cane" , "Carroll's sisters had to live with" .)