Doctor, say, has small bits left (5)
I believe the answer is:
dregs
'bits left' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'doctor say has small' is the wordplay.
'doctor' becomes 'dr' (abbreviation).
'say' becomes 'eg' (both can mean for example).
'has' is a charade indicator (letters next to each other).
'small' becomes 's' (abbreviation - e.g. clothes size).
'dr'+'eg'+'s'='DREGS'
Can you help me to learn more?
(Other definitions for dregs that I've seen before include "Wine or coffee residue" , "Lees - riffraff" , "Residue, lees" , "Most worthless part (of anything)" , "Sediment at bottom of drink" .)