Scot upset by expenditure (4)
I believe the answer is:
cost
'expenditure' is the definition.
(I know that cost is a type of expenditure)
'scot upset' is the wordplay.
'upset' indicates anagramming the letters.
'scot' with letters rearranged gives 'COST'.
'by' is the link.
(Other definitions for cost that I've seen before include "penalty" , "Outlay required to buy" , "Estimate the expense of doing" , "Come to" , "Fee" .)