Constitutionally lazy (4,4)
I believe the answer is:
bone idle
'constitutionally lazy' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for bone idle that I've seen before include "Extremely lazy" , "Not lifting a finger" , "staff may be?" , "Very, lazy, almost ossified" , "Very lazy from the inside out" .)