In part Louis toured a Hebridean island or two (4)
I believe the answer is:
uist
'hebridean island or two' is the definition.
(North Uist and South Uist in the Hebrides)
'in part louis toured a' is the wordplay.
'in part' says the answer is hidden in the clue.
'UIST' is hidden within 'louis toured a'.
(Other definitions for uist that I've seen before include "Hebridean islands, North and South ____" , "North and South islands of the Outer Hebrides" , "Hebridean island" .)