Remains doctors, for example, have (5)
I believe the answer is:
dregs
'remains' is the definition.
(I've seen this in another clue)
'doctors for example have' is the wordplay.
I cannot quite understand how this works, but
'example' could be 'eg' (short for 'exempli gratia', 'for example' in Latin) and 'eg' is present in the answer.
'doctors' could be 'drs' ('Dr' can be a synonym of 'doctor') and 'drs' is located in the leftover letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for dregs that I've seen before include "Wine or coffee residue" , "Sediment, lees" , "Wine sediment" , "What's left" , "Most worthless parts" .)