Hidden difficulty dangerous to miners (7)

I believe the answer is:

pitfall

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'hidden difficulty' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

(Other definitions for pitfall that I've seen before include "Trap in the form of a concealed hole" , "Unexpected difficulty or danger" , "Hidden danger or difficulty" , "Unsuspected danger or difficulty - for miner?" , "Hazard" .)

I've seen this clue in The Irish Independent.

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