Climbing a track (6)
I believe the answer is:
ascent
'climbing' is the definition.
(I've seen this before)
'a track' is the wordplay.
'track' becomes 'scent'.
'a'+'scent'='ASCENT'
(Other definitions for ascent that I've seen before include "made by Hilary and Tenzing" , "Hill" , "Going up" , "The climbing of a peak" , "Maybe promotion" .)