Doctor, for example, with small residue (5)
I believe the answer is:
dregs
'residue' is the definition.
(I've seen this in another clue)
'doctor for example with small' is the wordplay.
'doctor' becomes 'Dr' (abbreviation).
'for example' becomes 'e.g.' (short for 'exempli gratia', 'for example' in Latin).
'with' says to put letters next to each other.
'small' becomes 's' (abbreviation - e.g. clothes size).
'dr'+'eg'+'s'='DREGS'
(Other definitions for dregs that I've seen before include "Parts of least value" , "Leftover drink, sediment" , "Wine or coffee residue" , "Remaining sediment" , "Sediment - rabble" .)