Going up without a trail (5)
I believe the answer is:
scent
'trail' is the definition.
(thesaurus)
'going up without a' is the wordplay.
'going up' becomes 'ascent' (I've seen this before).
'without' suggests deleting specific letters.
'ascent' with 'a' taken away is 'SCENT'.
(Other definitions for scent that I've seen before include "Pleasant smell" , "Number of clues" , "Whiff" , "Distinctive aroma" , "Fragrance" .)