Technician denies power to ardent supporter (7)
I believe the answer is:
artisan
'technician' is the definition.
(thesaurus)
'denies power to ardent supporter' is the wordplay.
'denies' indicates named letters should be taken away.
'power' becomes 'p'.
'to ardent supporter' becomes 'partisan'.
'partisan' with 'p' taken away is 'ARTISAN'.
(Other definitions for artisan that I've seen before include "Technician" , "Smith" , "one in command of craft?" , "Skilled workman" , "craftsman of his trade" .)