Journey to the bar and back?
I believe the answer is:
I believe this clue is a double definition.
'journey' is the first definition.
(round trip is a kind of journey)
'the bar and back?' is the second definition.
(I've seen this before)
'to' acts as a link.
(Other definitions for round trip that I've seen before include "Two-way journey" , "excursion" , "collecting drinks from the bar?" , "orbit" , "Return journey" .)