A tax raised for Budget (5)
I believe the answer is:
allot
'budget' is the definition.
(I've seen this before)
'a tax raised' is the wordplay.
'tax' becomes 'toll' (I've seen this in another clue).
'raised' is a reversal indicator (going up in a down clue).
'toll' in reverse letter order is 'llot'.
'a'+'llot'='ALLOT'
'for' is the link.
(Other definitions for allot that I've seen before include "deal" , "Give as a share, or a task to be done" , "Apportion (something to someone)" , "Assign a share" , "Designate; sounds like much" .)