Grounds, for instance, accepted by doctors (5)
I believe the answer is:
dregs
'grounds' is the definition.
('dregs' can be a synonym of 'grounds')
'for instance accepted by doctors' is the wordplay.
'for instance' becomes 'eg' ('e.g.' can be a synonym of 'for instance').
'accepted by' indicates putting letters inside.
'doctors' becomes 'drs' ('Dr' can be a synonym of 'doctor').
'eg' going into 'drs' is 'DREGS'.
(Other definitions for dregs that I've seen before include "Sediment at the bottom of a liquid" , "Fluid remnants" , "Parts of least value" , "Most worthless part (of anything)" , "Sediment at bottom of drink" .)