Parking inside, remove exhaust (7)
I believe the answer is:
deplete
'exhaust' is the definition.
(I know that exhaust can be written as deplete)
'parking inside remove' is the wordplay.
'parking' becomes 'p' (abbreviation on road signs).
'inside' is an insertion indicator.
'remove' becomes 'delete' (deleting is a kind of removing).
'p' going within 'delete' is 'DEPLETE'.
(Other definitions for deplete that I've seen before include "Use up quantities of, reduce store" , "Reduce the quantity of (resources)" , "Reduce the number of" , "Use up a supply" , "Use up resources of" .)