Parking car heavy on petrol — gallons gone for you (7)
I believe the answer is:
puzzler
'you' is the definition.
(you are solving this puzzle!)
'parking car heavy on petrol gallons gone' is the wordplay.
'parking' becomes 'p' (abbreviation on road signs).
'car heavy on petrol' becomes 'guzzler' (a car which guzzles petrol).
'gallons' becomes 'g'.
'gone' suggests deleting specific letters.
'guzzler' with 'g' removed is 'uzzler'.
'p'+'uzzler'='PUZZLER'
'for' is the link.
(Other definitions for puzzler that I've seen before include "Something that perplexes" , "Confusing thing" , "Particularly baffling problem" , "Crossword solver?" .)