One attached to back language (5)
I believe the answer is:
hindi
'language' is the definition.
(Hindi is an example)
'one attached to back' is the wordplay.
'one' becomes 'i' (Roman numeral).
'attached to' is a charade indicator (letters next to each other).
'back' becomes 'hind' ('hind' can be a synonym of 'back'**).
'i' put after 'hind' is 'HINDI'.
(Other definitions for hindi that I've seen before include "language many use" , "Asian language" , "It's spoken abroad" , "An official language of India" , "tongue" .)