Revolutionary American monks' leader accepting European is better (8)
I believe the answer is:
superior
'is better' is the definition.
(thesaurus)
'revolutionary american monks' leader accepting european' is the wordplay.
'revolutionary' says the letters should be written backwards.
'american' becomes 'us'.
'monks' leader' becomes 'prior'.
'accepting' is an insertion indicator.
'european' becomes 'e' (abbreviation e.g. EU).
'us' reversed gives 'su'.
'prior' enclosing 'e' is 'perior'.
'su'+'perior'='SUPERIOR'
(Other definitions for superior that I've seen before include "Higher-ranking" , "head of monastery" , "Higher in position or rank" , "Higher ranking" , "A better boss?" .)