Small part of revolutionary poem acclaimed (5)
I believe the answer is:
cameo
'small part' is the definition.
(small part in a film)
'of revolutionary poem acclaimed' is the wordplay.
'revolutionary' is a reversal indicator.
'of' says the answer is hidden in the clue.
'oemac' can be found hidden inside 'poem acclaimed'.
'oemac' back-to-front is 'CAMEO'.
(Other definitions for cameo that I've seen before include "Small but interesting role" , "Ornament or miniature performance" , "Star's tiny role" , "Miniature picture" , "Brief role" .)