Cooker of very exquisite nosh (starters only) (4)
I believe the answer is:
oven
'cooker' is the definition.
(I've seen this before)
'of very exquisite nosh starters only' is the wordplay.
'starters only' indicates taking the first letters (the letters which start the words).
The first letters of 'of very exquisite nosh' is 'OVEN'.
(Other definitions for oven that I've seen before include "Place for burning" , "Chamber for baking" , "Part of a cooker" , "Section of a cooker" , "Kitchen appliance" .)