Argue about religious education cost (7)
I believe the answer is:
freight
'cost' is the definition.
(freight is a kind of cost)
'argue about religious education' is the wordplay.
'argue' becomes 'fight' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'about' indicates putting letters inside.
'religious education' becomes 're'.
'fight' going around 're' is 'FREIGHT'.
Can you help me to learn more?
(Other definitions for freight that I've seen before include "Cargo, goods transported" , "Consignment" , "Transport of bulk goods" , "Charge for carrying" , "Goods in transit" .)