Coat to protect sailor, old, visiting island in Med (8)
I believe the answer is:
creosote
'island in med' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'coat to protect sailor old visiting' is the wordplay.
'coat' becomes 'crete' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to protect' means one lot of letters goes inside another (inserted letters are protected or taken in).
'sailor' becomes 'os' (ordinary seaman).
'old' becomes 'o' (abbreviation).
'visiting' is an insertion indicator.
'crete' enclosing 'os' is 'creoste'.
'creoste' going around 'o' is 'CREOSOTE'.
Can you help me to learn more?
(Other definitions for creosote that I've seen before include "Dark oily liquid, preservative for wood" , "Wood treatment" , "Oily liquid for preserving timber" , "Oily excretion" , "Wood preserver made from coal tar" .)