National Front of Belfast tense with Irish revolutionary (7)
I believe the answer is:
british
'national' is the definition.
(from Great Britain)
'front of belfast tense with irish revolutionary' is the wordplay.
'front of' indicates taking the first letters.
'tense' becomes 't' (abbreviation used in many dictionaries).
'with' says to put letters next to each other.
'revolutionary' indicates anagramming the letters.
The initial letter of 'belfast' is 'b'.
't' after 'irish' is 'irisht'.
'irisht' anagrammed gives 'ritish'.
'b'+'ritish'='BRITISH'
(Other definitions for british that I've seen before include "M [MUSEUM]" , "Children's game -- our national mascot?" , "As people under a monarchy" , "Hits rib of this nationality" , "From the UK" .)