Climb a post, enthralling Charlie (6)
I believe the answer is:
ascend
'climb' is the definition.
(climb can mean to ascend or go up)
'a post enthralling charlie' is the wordplay.
'post' becomes 'send' (synonyms).
'enthralling' is an insertion indicator.
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'send' enclosing 'c' is 'scend'.
'a'+'scend'='ASCEND'
(Other definitions for ascend that I've seen before include "Scale" , "Make the top" , "Move upwards" , "Move upward" , "Gain altitude" .)