Clown, Greek character to work hard in cooking medium (7,3)

'cooking medium' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.

'clown greek character to work hard' is the wordplay.
'clown' becomes 'coco' (Nicolai Poliakoff aka Coco the Clown).
'greek character' becomes 'nu' (letter from the Greek alphabet).
'to work hard' becomes 'toil' (to toil is to do strenuous work).
'coco'+'nu'+'toil'='COCONUT-OIL'

'in' is the link.

Can you help me to learn more?