Maybe Protestant doctor desires to retain 24s (9)
I believe the answer is:
dissenter
'maybe protestant' is the definition.
I can't explain the rest of the clue.
(Other definitions for dissenter that I've seen before include "Nonconformist" , "One who disagrees out of tiredness" , "one not C of E" , "One not agreeing" , "One who disagrees among residents" .)