Mine to tip over (3)
I believe the answer is:
pit
'mine' is the definition.
(down the pit)
'tip over' is the wordplay.
'over' shows that the letters should be reversed in order.
'tip' written backwards gives 'PIT'.
'to' acts as a link.
(Other definitions for pit that I've seen before include "A hole as for coal" , "Mining hole" , "Quarry" , "Coalmine" , "Place for the accompanying orchestra" .)