Old Russians in tutus regularly adopting Indian garments (8)
I believe the answer is:
tsarists
'old russians' is the definition.
(supporters of the Russian tsars)
'tutus regularly adopting indian garments' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'adopting' means one lot of letters goes inside another (inserted letters are taken on or adopted).
'indian garments' becomes 'saris' (sari is a type of Indian garment).
The alternate letters of 'tutus' are 'tts'.
'tts' placed around 'saris' is 'TSARISTS'.
'in' is the link.
(Another definition for tsarists that I've seen is " Russian imperialists".)