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'm not sure about the 'so much' bit.
'in the underground section' is the wordplay.
'in' indicates a hidden word.
'ERG' is hidden in the letters of '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.)" .)