Jack, on the road with Mac (3)
I believe the answer is:
tar
'jack' is the definition.
(both are informal terms for sailor)
'the road with mac?' is the wordplay.
I cannot quite understand how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
The remaining letters 'ar' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'on' is the link.
Can you help me to learn more?
(Other definitions for tar that I've seen before include "Sailor and dressing for roads" , "Pitch; sailor" , "Art (anag.)" , "Slang sailor or road surfacing material" , "Dark viscous flammable substance" .)