Fellow artist regularly guides impostors (6)
I believe the answer is:
frauds
'impostors' is the definition.
('fraud' can be a synonym of 'impostor')
'fellow artist regularly guides' is the wordplay.
'fellow' becomes 'f' (abbreviation - of a society etc.).
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternating letters of 'guides' are 'uds'.
'f'+'ra'+'uds'='FRAUDS'
(Other definitions for frauds that I've seen before include "Criminal deceptions" , "Cheaters and swindlers" , "con merchants" .)