Language using play on words: "setter's on strike" (7)
I believe the answer is:
punjabi
'language' is the definition.
(Punjabi is an example)
'play on words setter's on strike' is the wordplay.
'play on words' becomes 'pun' (synonyms).
'setter' becomes 'I' (the person who set this crossword).
'on' says to put letters next to each other.
'strike' becomes 'jab' (jabbing is a kind of striking).
'i' put after 'jab' is 'jabi'.
'pun'+'jabi'='PUNJABI'
'using' is the link.
(Other definitions for punjabi that I've seen before include "Indian language" , "Native of region shared by India and Pakistan" , "From NW India" , "Asian language" , "tongue" .)