Pitch into Jolly Jack! (3)
I believe the answer is:
tar
I believe this is a double definition.
'pitch' is the first definition.
(synonyms)
'jolly jack' is the second definition.
(Jolly Jack Tar can mean a sailor)
'into' acts as a link.
(Other definitions for tar that I've seen before include "Cigarette substance" , "Sailor (colloq.)" , "It paves the way" , "Naval man" , "Familiar sailor - what a rat" .)