Children, those working down the pit, we hear? (6)

I believe the answer is:

minors

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'children' is the definition.
(I know this)

I can't explain the remainder of the clue.

(Other definitions for minors that I've seen before include "They're under-age" , "They're too young to vote" , "They are legally under-age" , "could be little ones" , "Young people" .)

I've seen this clue in The Times.

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