Guide people over hill (6)
I believe the answer is:
mentor
'guide' is the definition.
(thesaurus)
'people over hill' is the wordplay.
'people' becomes 'men' (man is a kind of person).
'over' means one lot of letters go next to another.
'hill' becomes 'tor' (tor is a kind of hill).
'men'+'tor'='MENTOR'
(Other definitions for mentor that I've seen before include "Merton (anag.)" , "He advises" , "A wise and learned teacher" , "Wise and trusted adviser" , "Guru" .)