Miners embracing underworld in public exposure (6)
I believe the answer is:
nudism
'public exposure' is the definition.
(I've seen this before)
'miners embracing underworld' is the wordplay.
'miners' becomes 'num'.
'embracing' means one lot of letters goes inside another.
'underworld' becomes 'dis' (I've seen this before).
'num' going around 'dis' is 'NUDISM'.
'in' is the link.
(Other definitions for nudism that I've seen before include "taking off habitually" , "Practice of going without clothes" , "Practice of living as nature intended" , "Going without clothes, socially" , "Pursuit of a naturist" .)