Amount of work produced from the power generator (3)
I believe the answer is:
erg
'amount of work' is the definition.
(scientific unit for work or energy)
'from the power generator' is the wordplay.
'from' indicates the answer is hidden within the clue.
'ERG' is hidden in the letters of 'power generator'.
'produced' is the link.
(Other definitions for erg that I've seen before include "shifting sand" , "What's used to record work" , "Unit of measurement of work" , "Unit of work or energy" , "Unit of work; dunes area" .)