Guide soldiers approaching hill (6)
I believe the answer is:
mentor
'guide' is the definition.
(thesaurus)
'soldiers approaching hill' is the wordplay.
'soldiers' becomes 'men' (I've seen this before).
'approaching' says to put letters next to each other.
'hill' becomes 'tor' (tor is a kind of hill).
'men'+'tor'='MENTOR'
(Other definitions for mentor that I've seen before include "Merton (anag.)" , "Wise and trusted adviser" , "A trusted teacher or counsellor" , "Personal guide" , ""Guide, philosopher, and friend"" .)