Asian garments adopted by abstemious old Russian (7)
I believe the answer is:
tsarist
'old russian' is the definition.
'tsarist' can be an answer for 'russian' (I've seen this before). I'm not sure about the 'old' bit.
'asian garments adopted by abstemious' is the wordplay.
'asian garments' becomes 'saris' (I've seen this in another clue).
'adopted by' indicates putting letters inside (I've seen this in other clues).
'abstemious' becomes 'tt' (I've seen this in other clues).
'saris' inserted within 'tt' is 'TSARIST'.
Can you help me to learn more?
(Other definitions for tsarist that I've seen before include "One supporting ruler" , "Of emperors of old Russia" , "Artists (anag.); supporter of Russian emperor" , "Bolshevik opponent" , "Supporter of the Russian Empire" .)