Persian is taking service back (5)
I believe the answer is:
farsi
'persian' is the definition.
(Farsi is an example)
'is taking service back' is the wordplay.
'taking' means one lot of letters go next to another.
'service' becomes 'raf'.
'back' says the letters should be written backwards.
'is'+'raf'='israf'
'israf' written backwards gives 'FARSI'.
(Other definitions for farsi that I've seen before include "Language of Iran" , "Modern Persian lang." , "foreign language" , "Iran's official language" , "Persian language" .)