Hidden difficulty caused by subsidence in mine (7)
I believe the answer is:
pitfall
This might be a double definition.
'hidden difficulty' is the first definition.
(I've seen this before)
'subsidence in mine' is the second definition.
'pitfall' can be an answer for 'mine' (thesaurus). I am not certain of the 'subsidence in' bit.
'caused by' acts as a link.
Can you help me to learn more?
(Other definitions for pitfall that I've seen before include "Unforeseen difficulty" , "Unexpected problem" , "Trap in the form of a concealed hole" , "Hidden danger or difficulty" , "Unsuspected danger or difficulty - for miner?" .)