Protective covering casts a marina out (12)
I believe the answer is:
antimacassar
'protective covering' is the definition.
'antimacassar' can be an answer for 'covering' (antimacassar is a kind of covering). I'm unsure of the 'protective' bit.
'casts a marina out' is the wordplay.
'out' is an anagram indicator (out can mean wrong or inaccurate).
'casts'+'a'+'marina'='castsamarina'
'castsamarina' with letters rearranged gives 'ANTIMACASSAR'.
Can you help me to learn more?
(Other definitions for antimacassar that I've seen before include "Covering to protect the back of a chair from hair oils" , "Protective chair cover" , "It keeps hair oil off the back of a chair" , "Protective cloth on upholstered seat" , "Cloth protecting chair from grease" .)