Praise revolutionary Iran once (6)
I believe the answer is:
persia
'iran once' is the definition.
(I've seen this before)
'praise revolutionary' is the wordplay.
'revolutionary' indicates an anagram.
'praise' is an anagram of 'PERSIA'.
(Other definitions for persia that I've seen before include "Old land" , "Old name for country at 25 Across" , "Iran, formerly" , "Praise be to ancient Iran" , "Old Iran" .)