Clamber (8)
I believe the answer is:
scramble
'clamber' is the definition.
(I know that clamber can be written as scramble)
This is the entire clue.
(Other definitions for scramble that I've seen before include "keep communication secret" , "make breakfast, perhaps" , "To clamber or climb" , "Muddle up" , "Motorbike rally" .)