Spa cover (4)
I believe the answer is:
robe
'spa cover' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for robe that I've seen before include "Ceremonial garb" , "judge's garment" , "Long loose garment or dressing gown" , "Formal gown" , "Christening garment" .)