Couple can tour Western Australia (5)
I believe the answer is:
twain
'couple' is the definition.
(archaic term for 'two')
'can tour western australia' is the wordplay.
I cannot quite see how this works, but
'western' could be 'w' and 'w' is found within the answer.
'australia' could be 'a' (abbreviation for Australia) and 'a' is located in the answer.
'can' could be 'tin' (both are metal containers) and 'tin' is found within the leftover letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for twain that I've seen before include "Old pair beginning" , "A pen-name" , "Mark ..... created Tom Sawyer" , "Mark ..... created Huckleberry Finn" , "Mark -, Huckleberry Finn author" .)