Approve climb, we hear? (6)
I believe the answer is:
assent
'approve' is the definition.
(thesaurus)
'climb we hear?' is the wordplay.
'climb' becomes 'ascent' ('ascent' can be a synonym of 'climb').
'we hear?' indicates a 'sounds like' (homophone) clue.
'ascent' is a homophone of 'ASSENT'.
(Other definitions for assent that I've seen before include "Agree and concur" , "Nod" , "Give consent" , "Agree - concede" , "Express approval or agreement" .)