Go-ahead for climb discussed (6)
I believe the answer is:
assent
'go-ahead' is the definition.
(I've seen this in another clue)
'climb discussed' is the wordplay.
'climb' becomes 'ascent' (synonyms).
'discussed' indicates a 'sounds like' (homophone) clue.
'ascent' sounds like 'ASSENT'.
'for' is the link.
(Other definitions for assent that I've seen before include "Compliance, agreement" , "Official sanction" , "Expression of agreement" , "Nod" , "Acquiescence" .)