They shouldn't be drunk, for example, when doctors are around (5)
I believe the answer is:
dregs
'they shouldn't' is the definition.
The definition suggests a singular noun which matches the answer.
'drunk for example when doctors are around' is the wordplay.
I cannot really understand how this works, but
'example' could be 'eg' (short for 'exempli gratia', 'for example' in Latin) and 'eg' is located in the answer.
'doctors' could be 'drs' ('Dr' can be a synonym of 'doctor') and 'drs' is found within the remaining letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'be' is the link.
Can you help me to learn more?
(Other definitions for dregs that I've seen before include "Fluid remnants" , "Residue, lees" , "Grounds; refuse" , "Sediment at bottom of drink" , "What's left" .)