Cook is engaged by Scottish bank (6)
I believe the answer is:
braise
'cook' is the definition.
(braising is a kind of cooking)
'is engaged by scottish bank' is the wordplay.
'engaged by' means one lot of letters goes inside another (I've seen this in other clues).
'scottish bank' becomes 'brae' (I've seen this before).
'is' placed into 'brae' is 'BRAISE'.
(Other definitions for braise that I've seen before include "Heat slowly" , "Re bias (anag.)" , "Fry then stew (meat)" , "Fry and then stew (food)" , "Rabies (anag.)" .)