Switched on tailors for barbers (9)
I believe the answer is:
tonsorial
'for barbers' is the definition.
(tonsorial means relating to hairdressing)
'switched on tailors' is the wordplay.
'switched' indicates anagramming the letters (letters switch places).
'on'+'tailors'='ontailors'
'ontailors' with letters rearranged gives 'TONSORIAL'.
(Other definitions for tonsorial that I've seen before include "Barber's" , "for barber" , "using scissors for work?" .)