Anger unknown by a revolutionary Eurasian (5)
I believe the answer is:
azeri
'eurasian' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'anger unknown by a revolutionary' is the wordplay.
'anger' becomes 'ire' (ire is intense rage).
'unknown' becomes 'z' (algebra).
'by' says to put letters next to each other.
'revolutionary' is a reversal indicator (letters revolve around).
'ire'+'z'+'a'='ireza'
'ireza' back-to-front is 'AZERI'.
Can you help me to learn more?
(Other definitions for azeri that I've seen before include "Someone in Baku" , "Foreign citizen" , "Caucasian" , "Asian" , "foreign language" .)