Wire barrier across path restricts hill climbing (7)
I believe the answer is:
garotte
'wire' is the definition.
(wire used to strangle someone)
'barrier across path restricts hill climbing' is the wordplay.
'barrier across path' becomes 'gate' (barrier at the end of a path).
'restricts' indicates putting letters inside.
'hill' becomes 'tor' (tor is a kind of hill).
'climbing' says the letters should be written in reverse (in a down clue, letters climb up).
'tor' reversed gives 'rot'.
'gate' placed around 'rot' is 'GAROTTE'.
(Other definitions for garotte that I've seen before include "Kill by strangulation" , "Strangle" , "Spanish method of execution" , "throttle" , "Facility to dispose of person" .)