Mass run on maintenance cost (7,6)
I believe the answer is:
service charge
'cost' is the definition.
(service charge is a kind of cost)
'mass run on maintenance' is the wordplay.
'mass run' becomes 'charge' (I am not sure about the 'mass' bit.).
'on' is a charade indicator (letters next to each other).
'maintenance' becomes 'service' (service is a kind of maintenance).
'charge' after 'service' is 'SERVICE CHARGE'.
Can you help me to learn more?
(Other definitions for service charge that I've seen before include "Restaurant bill addition" , "Additional restaurant fee" , "Restaurant bill add-on" , "Restaurant may have one" , "Percentage added to the bill?" .)