Some sash entirely grey (5)
I believe the answer is:
ashen
'grey' is the definition.
(I've seen this before)
'some sash entirely' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'ASHEN' can be found hidden inside 'sash entirely'.
(Other definitions for ashen that I've seen before include "(Of face) pale with fear" , "Having gone pale" , "Wan, pale" , "may be pale with shock" , "Pale (faced)" .)