Paving gunk (3)
I believe the answer is:
tar
'paving gunk' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tar that I've seen before include "Mariner, old salt" , "'Thick, dark, sticky liquid (3)'" , "Sailor - laid on road" , "Black substance, used on roads" , "Jack ..., British sailor" .)