Left mine entrance heading north, like some rivers (5)
I believe the answer is:
tidal
'like some rivers' is the definition.
(I've seen this in another clue)
'left mine entrance heading north' is the wordplay.
'left' becomes 'L' (common abbreviation).
'mine entrance' becomes 'adit' (I've seen this before).
'heading north' shows that the letters should be reversed in order.
'l'+'adit'='ladit'
'ladit' in reverse letter order is 'TIDAL'.
(Other definitions for tidal that I've seen before include "going with the flow" , "Relating to ocean surges" , "Going back and forth" , "Relating to the flow of the sea" , "Of ebbs and flows" .)