New climb beginning (7)
I believe the answer is:
nascent
'beginning' is the definition.
(I've seen this before)
'new climb' is the wordplay.
'new' becomes 'n'.
'climb' becomes 'ascent' ('ascent' can be a synonym of 'climb').
'n'+'ascent'='NASCENT'
(Other definitions for nascent that I've seen before include "Dawning" , "Freshly generated" , "Starting to develop" , "Incipient" , "not yet mature" .)