Tourist; one on an excursion (7)
I believe the answer is:
tripper
I believe this clue is a double definition.
'tourist' is the first definition.
(I know that tripper is a type of tourist)
'one on an excursion' is the second definition.
(I've seen this before)
(Other definitions for tripper that I've seen before include "who might get a booking?" , "One hoping to enjoy journey" , "Motorist just for fun" , "Excursionist" , "Someone out for day" .)