Rather large robes employed, but not all (5)
I believe the answer is:
obese
'rather large' is the definition.
'robes employed but not all' is the wordplay.
'not all' indicates a hidden word.
'OBESE' is hidden in the letters of 'robes employed but'.
(Other definitions for obese that I've seen before include "Extremely overweight" , "Extremely portly" , "Dangerously corpulent" , "in need of slimming down" , "Too chubby" .)