Travelled south across hot island (6)
I believe the answer is:
rhodes
'island' is the definition.
(Greek island)
'travelled south across hot' is the wordplay.
'travelled' becomes 'rode' (eg travelled on a horse).
'south' becomes 's' (abbreviation).
'across' is an insertion indicator.
'hot' becomes 'h' (abbreviation eg on taps).
'rode'+'s'='rodes'
'rodes' going around 'h' is 'RHODES'.
(Other definitions for rhodes that I've seen before include "British financier and coloniser in southern Africa, d. 1902" , "Largest island of the Dodecanese" , "Hordes go to the Greek island" , "Greek island - British-born South African statesman" , "Island, explorer" .)