Ruin what's left of ship (5)
I believe the answer is:
wreck
This clue might be a double definition.
'ruin' is the first definition.
(I know that wreck is a more specific form of the action ruin)
'left of ship' is the second definition.
'wreck' can be an answer for 'ship' (wreck is a kind of ship). I am not sure about the 'left of' bit.
'what's' is the link.
Can you help me to learn more?
(Other definitions for wreck that I've seen before include "A destroyed ship" , "Destroy; sunken vessel" , "Completely spoil" , "Destroy, ruin" , "Ruin; shatter" .)