A line she’s rewritten in Sri Lankan language (9)
I believe the answer is:
sinhalese
'sri lankan language' is the definition.
(Sinhalese is a language of Sri Lanka)
'a line she's rewritten' is the wordplay.
'rewritten' is an anagram indicator.
'a'+'line'+'shes'='alineshes'
'alineshes' anagrammed gives 'SINHALESE'.
'in' is the link.
(Other definitions for sinhalese that I've seen before include "language" , "Sri Lankan" .)