So much work in the underground section (3)
I believe the answer is:
erg
'so much work' is the definition.
'erg' can be an answer for 'work' (an erg is a unit of work done). I am not certain of the 'so much' bit.
'in the underground section' is the wordplay.
'in' says the answer is hidden in the clue.
'ERG' can be found hidden inside 'underground section'.
Can you help me to learn more?
(Other definitions for erg that I've seen before include "Unit of work; dunes area" , "Unit of measurement of work" , "Energy expended" , "Unit of work or energy" , "Unit of work (phys.)" .)