Item climber starting off over slope has on for support? (7)
I believe the answer is:
crampon
'item climber starting off over' is the definition.
I can't judge whether this defines the answer.
'slope has on for support?' is the wordplay.
'slope' becomes 'ramp' (I've seen this before).
'has' means one lot of letters go next to another.
'for' means one lot of letters go next to another (I've seen this in other clues).
'support?' becomes 'c' (I can't explain this - if you can you should give a lot more credence to this answer).
'ramp'+'on' is 'rampon'.
'rampon' put after 'c' is 'CRAMPON'.
(Other definitions for crampon that I've seen before include "Spiked attachment for climbing boot" , "Spiked plate for a climbing boot" , "Grappling iron" , "Gripping device" , "Climber's boot spikes" .)