Decent amount to clear up problem? (4,3)
I believe the answer is:
tidy sum
'decent amount' is the definition.
(a decent amount of money)
'clear up problem?' is the wordplay.
'clear up' becomes 'tidy' (I've seen this before).
'problem?' becomes 'sum' (arithmetic problem).
'tidy'+'sum'='TIDY SUM'
'to' acts as a link.
(Other definitions for tidy sum that I've seen before include "Considerable amount" , "A lot of money" .)