Not sure about coatings (8)
I believe the answer is:
agnostic
'not sure' is the definition.
(I've seen this before)
'about coatings' is the wordplay.
'about' is an anagram indicator.
'coatings' is an anagram of 'AGNOSTIC'.
(Other definitions for agnostic that I've seen before include "someone like Pyrrho" , "One doubts" , "Song I act (anag)" , "Coasting away with non-believer" , "Don't know" .)