What a piece of work! (3)
I believe the answer is:
erg
'what a piece of work' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for erg that I've seen before include "What's used to record work" , "Energy expended" , "Unit of work; dunes area" , "Amount of work" , "Unit of work or energy" .)