Verbal agreement resulting in promotion (6)
I believe the answer is:
ascent
'promotion' is the definition.
(I've seen this before)
'verbal agreement' is the wordplay.
'verbal' shows a homophone (sound like).
'agreement' becomes 'assent' (assent is a kind of agreement).
'assent' is a homophone of 'ASCENT'.
'resulting in' is the link.
(Other definitions for ascent that I've seen before include "Hill" , "Enacts in climb" , "An up-slope" , "advancement" , "made by Hilary and Tenzing" .)