Guide chaps on mountain (6)
I believe the answer is:
mentor
'guide' is the definition.
(I've seen this before)
'chaps on mountain' is the wordplay.
'chaps' becomes 'men' (I've seen this before).
'on' says to put letters next to each other.
'mountain' becomes 'tor'.
'men'+'tor'='MENTOR'
(Other definitions for mentor that I've seen before include "Truster advisor" , "A trusted adviser or teacher" , "Experienced adviser" , "Wise and experienced counsellor" , "Guru" .)