Person making a claim before proposal (9)
I believe the answer is:
pretender
'person making a claim' is the definition.
(eg someone making a claim to the throne)
'before proposal' is the wordplay.
'before' becomes 'pre' (prefix meaning 'before').
'proposal' becomes 'tender' (I've seen this before).
'pre'+'tender'='PRETENDER'
(Other definitions for pretender that I've seen before include "One acting" , "Claimant to a throne, usually without just title" , "fake" , "One claiming a title" , "One who claims a title or position" .)