Exorbitant demand for payment from drivers in Scotland known to cross river (4-4)
I believe the answer is:
rack-rent
'drivers in scotland known to cross river' is the definition.
I can't tell whether this defines the answer.
'exorbitant demand for payment' is the wordplay.
'exorbitant demand for' becomes 'rack' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'payment' becomes 'rent' (rent is a kind of payment).
'rack'+'rent'='RACK-RENT'
'from' is the link.
Can you help me to learn more?
(Other definitions for rack-rent that I've seen before include "Extortionate payment demanded from a tenant" , "What a predatory landlord charges" , "Extortionate amount charged for letting" , "Excessively high charge by landlord" .)