Rent is audibly increased (4)
I believe the answer is:
hire
'rent' is the definition.
(rent can mean to hire something out)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for hire that I've seen before include "Engage; rent" , "Rent, employ" , "Employ (for wages)" , "Charter, employ" , "Pay to use something" .)