Note English verb (reflexive) (5)
I believe the answer is:
breve
'note' is the definition.
(thesaurus)
'english verb reflexive' is the wordplay.
'english' becomes 'e' (abbreviation).
'reflexive' shows that the letters should be reversed in order.
'e'+'verb'='everb'
'everb' backwards is 'BREVE'.
(Other definitions for breve that I've seen before include "Rarely used musical note" , "Long note (mus.)" , "Accent - musical note" , "Note with the time value of eight crotchets" , "Long musical note" .)