Smart leaders of the revolution in Moscow (4)
I believe the answer is:
trim
'smart' is the definition.
('trim' can be a synonym of 'smart')
'leaders of the revolution in moscow' is the wordplay.
'leaders of' indicates taking the first letters.
The first letters of 'the revolution in moscow' is 'TRIM'.
(Other definitions for trim that I've seen before include "in good condition" , "Neat and orderly" , "Make neat and smooth by cutting, say hair" , "Neat - crop" , "Clip into shape" .)