Completing the tour with nothing else to do? (2,3,4,6)
I believe the answer is:
in the last resort
'completing the tour with nothing' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'else to do?' is the wordplay.
I cannot quite see how this works, but
'else' could be 'or' (I've seen this in another clue) and 'or' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for in the last resort that I've seen before include "finishing off a tour?" , "having no other hope of help?" , "Where one spent the previous holiday" , "Using desperate expedient" , "When all else fails" .)