Cost of transport spoils date (7)
I believe the answer is:
haulage
'cost of transport' is the definition.
(cost of transporting gods)
'spoils date' is the wordplay.
'spoils' becomes 'haul' (I've seen this in another clue).
'date' becomes 'age' (both can mean to get older).
'haul'+'age'='HAULAGE'
(Other definitions for haulage that I've seen before include "Road transport" , "Transport business" , "Commercial transport of goods" , "Commercial transportation of goods" , "Transportation of heavy goods" .)