A charge exists for hiring them
I believe the answer is:
taxis
'hiring them' is the definition.
I can't tell whether this defines the answer.
'a charge exists' is the wordplay.
'a charge' becomes 'tax' (tax is a kind of charge).
'exists' becomes 'is' ('be' can be a synonym of 'exist').
'tax'+'is'='TAXIS'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for taxis that I've seen before include "Cabs" , "return to right place" , "Cars with a driver for hire" .)