Failed actor sore about British language (5-5)
I believe the answer is:
serbo-croat
'language' is the definition.
(Serbo-Croat is an example)
'failed actor sore about british' is the wordplay.
'failed' indicates anagramming the letters.
'about' is an insertion indicator.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'actor'+'sore'='actorsore'
'actorsore' with letters rearranged gives 'serocroat'.
'serocroat' enclosing 'b' is 'SERBO-CROAT'.
(Other definitions for serbo-croat that I've seen before include "language" , "European" .)