Go slowly in tug (4)
I believe the answer is:
drag
I believe this clue is a double definition.
'go slowly' is the first definition.
(I've seen this in another clue)
'tug' is the second definition.
(thesaurus)
'in' acts as a link.
(Other definitions for drag that I've seen before include "Bind" , "such a nuisance" , "Pull along roughly" , "A bore (colloq.); lug" , "Pull - dredge - transvestite habit" .)