Congratulations! (4,4)
I believe the answer is:
well done
'congratulations' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for well done that I've seen before include "Congratulations - certainly not rare!" , "Commendation for achievement" , "Water supply fixed?" , "Bravo!" , "how you might get the chop" .)