Towards the top of a slope (6)
I believe the answer is:
uphill
'towards the top of a slope' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for uphill that I've seen before include "Difficult (struggle)" , "Difficult, like steep slope" , "Towards a slope's top" , "Laborious as for walker" , "The harder way to walk" .)