Auditor’s agreement to make progress (6)
I believe the answer is:
ascent
'progress' is the definition.
(I've seen this before)
'auditor's agreement' is the wordplay.
'auditor's' shows a homophone (sound like).
'agreement' becomes 'assent' (assent is a kind of agreement).
'assent' is a homophone of 'ASCENT'.
'to make' is the link.
(Other definitions for ascent that I've seen before include "Uphill journey" , "A rise in status; climb" , "Upwards motion" , "(A) climb (up mountain)" , "Hill" .)