It helps climber no end on way up (5)
I believe the answer is:
piton
'it helps climber' is the definition.
The definition suggests a singular noun which matches the answer.
'no end on way up' is the wordplay.
'end' becomes 'tip' (tip is a kind of end).
'on way up' says the letters should be written in reverse.
'no'+'tip'='notip'
'notip' back-to-front is 'PITON'.
Can you help me to learn more?
(Other definitions for piton that I've seen before include "What mountaineer requires" , "Mountaineer's metal spike" , "Climber's tool" , "In top (anag.)" , "Spiked climbing aid" .)