Expression of surprise chef hasn’t finished (3)
I believe the answer is:
coo
'expression of surprise' is the definition.
(I've seen this before)
'chef hasn't finished' is the wordplay.
'chef' becomes 'cook' (I've seen this before).
'hasn't finished' means to remove the last letter.
'cook' with its final letter taken away is 'COO'.
(Other definitions for coo that I've seen before include "well I never!" , "Goodness me!" , "Soft sound of dove or baby" , "Dove-like noise" , "Soft murmuring sound of a pigeon" .)