Bad thing to rock this gravy dish (4)
I believe the answer is:
boat
I believe this clue is a double definition.
'bad thing to rock' is the first definition.
(I've seen this in another clue)
'this gravy dish' is the second definition.
(I've seen this in another clue)
(Other definitions for boat that I've seen before include "Contest on the Thames" , "Vehicle for travelling over water" , "Water craft" , "Small vessel" , "See 1" .)