Hint mine will return (3)
I believe the answer is:
tip
'hint' is the definition.
(I know that hint can be written as tip)
'mine will return' is the wordplay.
'mine' becomes 'pit' (down the pit).
'will return' is a reversal indicator.
'pit' in reverse letter order is 'TIP'.
(Other definitions for tip that I've seen before include "Point; piece of advice" , "expected by those who wait" , "Helpful information; end" , "Dump; hint" , "Hint or dumping ground" .)