Unexciting European, dull revolutionary (4)
I believe the answer is:
tame
'unexciting' is the definition.
('tame' can be similar in meaning to 'unexciting')
'european dull revolutionary' is the wordplay.
'european' becomes 'e' (abbreviation e.g. EU).
'dull' becomes 'mat' ('mat' can be similar in meaning to 'dull').
'revolutionary' says the letters should be written backwards.
'e'+'mat'='emat'
'emat' back-to-front is 'TAME'.
(Other definitions for tame that I've seen before include "Domesticated - dull" , "Not exciting; domesticate" , "Domisticated with meat" , "'Domesticated, docile (4)'" , "Domesticated kind of meat" .)