Grey coat, out of place in class (8)
I believe the answer is:
category
'class' is the definition.
(I know that class can be written as category)
'grey coat out of place' is the wordplay.
'out of place' is an anagram indicator.
'grey'+'coat'='greycoat'
'greycoat' anagrammed gives 'CATEGORY'.
'in' is the link.
(Other definitions for category that I've seen before include "Class, group" , "Class of grey coat" , "Genre" , "Class or division of similar subjects" , "Logical grouping" .)