Alec's prepared to climb (5)
I believe the answer is:
scale
'climb' is the definition.
(scaling is a kind of climbing)
'alec's prepared' is the wordplay.
'prepared' indicates anagramming the letters.
'alecs' with letters rearranged gives 'SCALE'.
'to' acts as a link.
(Other definitions for scale that I've seen before include "Notes < magnitude" , "Ratio of, say, map to reality" , "Alec's (anag) -- graduation" , "Group of notes in ascending or descending order" , "Size ratio; skin flake" .)