CGS unit of work or energy (3)
I believe the answer is:
erg
I believe this clue is a double definition.
'cgs unit of work' is the first definition.
(I've seen this in another clue)
'energy' is the second definition.
(Other definitions for erg that I've seen before include "shifting sand" , "Unit of work or energy" , "Unit of work; dunes area" , "Amount of work" , "What's used to record work" .)