Stop doctor and answer (4)
I believe the answer is:
whoa
'stop' is the definition.
(I've seen this before)
'doctor and answer' is the wordplay.
'doctor' becomes 'who' (I've seen this in other clues).
'and' is a charade indicator (letters next to each other).
'answer' becomes 'a' (abbreviation eg in Q and A).
'who'+'a'='WHOA'
(Other definitions for whoa that I've seen before include "The King of rock and roll" , "halt" , "Command for horse to slow or stop" , "Order (horse) to stop" , "Stop, Dobbin!" .)