Thoroughly cooked, good job! (4,4)
I believe the answer is:
well done
I believe this clue is a double definition.
'thoroughly cooked' is the first definition.
(I've seen this before)
'good job' is the second definition.
(both might be said to acknowledge an achievement)
(Other definitions for well done that I've seen before include "Water supply fixed?" , "Far from rare" , "Commendation for achievement" , "expression of approval" , "How one might like one's steak?" .)