Subordinate underground worker, we hear? (5)
I believe the answer is:
minor
'subordinate' is the definition.
(thesaurus)
'underground worker we hear?' is the wordplay.
'underground worker' becomes 'miner' (I've seen this before).
'we hear?' shows a homophone (sound like).
'miner' is a homophone of 'MINOR'.
(Other definitions for minor that I've seen before include "Young person below voting age" , "Deceptively realistic (art)" , "Less important" , "One hasn't reached legal majority" , "Insignificant" .)