The one set in the ship is more erotic (8)
I believe the answer is:
steamier
'more erotic' is the definition.
(I've seen this in another clue)
'the one set in the ship' is the wordplay.
'the one' becomes 'i' (Roman numeral).
'set in' indicates putting letters inside.
'the ship' becomes 'steamer' (a steam ship).
'i' going within 'steamer' is 'STEAMIER'.
'is' acts as a link.
(Other definitions for steamier that I've seen before include "Comparatively hot and humid" , "more like a sauna" .)