Ride ship on e.g. ocean wave (6,7)
I believe the answer is:
roller coaster
'e g ocean wave' is the definition.
I can't tell whether this definition defines the answer.
'ride ship on' is the wordplay.
'ride' becomes 'coaster' (I can't justify this - if you can you should believe this answer much more).
'ship' becomes 'roller' (historical unsuccessful type of ship).
'on' says to put letters next to each other.
'coaster' after 'roller' is 'ROLLER-COASTER'.
(Other definitions for roller coaster that I've seen before include "Big dipper" , "Fairground attraction" , "It can produce lots of violent lurches" , "Series of emotional swings" , "Switchback" .)