Extremely lazy (4,4)
I believe the answer is:
bone idle
'extremely lazy' is the definition.
(bone idle means very lazy)
This is all the clue.
(Other definitions for bone idle that I've seen before include "Really lazy in ossified way" , "Extremely lazy" , "Very lazy, from the marrow out" , "Very lazy, may be ossified?" , "Not lifting a finger" .)