Asserts aristocrat is sheltering enemy of the revolution? (7)
I believe the answer is:
tsarist
'enemy of the revolution?' is the definition.
'asserts aristocrat is sheltering' is the wordplay.
'is sheltering' says the answer is hidden in the clue.
'TSARIST' is hidden within 'asserts aristocrat'.
(Other definitions for tsarist that I've seen before include "Supporter of the Russian Empire" , "Russian emperor's supporter" , "Of emperors of old Russia" , "Russian royal supporter" , "Russian royalist" .)