Almost certain to offer to concede (9)
I believe the answer is:
surrender
'concede' is the definition.
(I've seen this before)
'almost certain to offer' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'certain' becomes 'sure' ('sure' can be a synonym of 'certain').
'to offer' becomes 'render'.
'sure' with its last letter taken away is 'sur'.
'sur'+'render'='SURRENDER'
'to' acts as a link.
(Other definitions for surrender that I've seen before include "Yield - release" , "Cease resistance" , "Yield, give in" , "Cede" , "Hand over" .)