Roofing gunk (3)
I believe the answer is:
tar
'roofing 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 "Road-dressing for a sailor?" , "Informal sailor or road-surfacing material" , "one may need to pay on boat" , "Kind of rat for sailor" , "Old salt or liquid from coal" .)