Ruler involved in crimes after revolution (4)
I believe the answer is:
emir
'ruler' is the definition.
(emir is a kind of ruler)
'involved in crimes after revolution' is the wordplay.
'involved in' says the answer is hidden in the clue.
'after revolution' shows that the letters should be reversed in order.
'rime' is hidden within 'crimes'.
'rime' back-to-front is 'EMIR'.
(Other definitions for emir that I've seen before include "Eastern chieftain" , "Muslim ruler stuck in mire" , "Arab ruler" , "Islamic ruler" , "Middle-Eastern ruler" .)