One causes hurt, getting soldiers trapped between two hills (9)
I believe the answer is:
tormentor
'one causes hurt' is the definition.
(someone who torments others)
'soldiers trapped between two hills' is the wordplay.
'soldiers' becomes 'men' (men can mean a group of soldiers).
'trapped between' means one lot of letters goes inside another.
'two' says to double the letters.
'hills' becomes 'tor' (tor is a kind of hills).
'tor' doubled is 'tortor'.
'men' placed inside 'tortor' is 'TORMENTOR'.
'getting' acts as a link.
(Other definitions for tormentor that I've seen before include "One harassing" , "cause of suffering" , "Inflictor of pain or anguish" , "Bully" , "Person causing" .)