Doctors jokes told by Jonathan Ross? (6)
I believe the answer is:
quacks
'doctors' is the definition.
(quack is a kind of doctor)
I don't understand how the rest of the clue works.
(Other definitions for quacks that I've seen before include "Ducks' noises" , "They are unqualified to deal with complaints" , "Makes sounds like a duck" , "Duck sounds or dud doctors" , "Bad doctors or duck sounds" .)