Rental is increased, we hear (4)
I believe the answer is:
hire
'rental' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for hire that I've seen before include "Pay to use something" , "Rent, employ" , "Pay for temporary use" , "Employ (for wages)" , "Payment for use" .)