Proposal for volunteer? (5)
I believe the answer is:
offer
This clue is a double definition.
'proposal' is the first definition.
(I've seen this in other clues)
'volunteer?' is the second definition.
('offer' can be a synonym of 'volunteer')
'for' is the link.
(Other definitions for offer that I've seen before include "Sum of money proposed as payment" , "hand" , "Propose (to give)" , "Attempt" , "Proposal; reduced price" .)