Officer and monarch useful at cookery (8)
I believe the answer is:
colander
'useful at cookery' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'officer and monarch' is the wordplay.
'officer' becomes 'col' (short for colonel).
'monarch' becomes 'ER' (abbreviation for Elizabeth Regina).
'col'+'and'+'er'='COLANDER'
Can you help me to learn more?
(Other definitions for colander that I've seen before include "Bowl-shaped strainer" , "found in the kitchen" , "Boiled 20 Down may be strained through this" , "Utensil for draining vegetables" , "Old crane (anag.)" .)