Language used by writer's expressive (4)
I believe the answer is:
erse
'language' is the definition.
(Erse is an example)
'used by writer's expressive' is the wordplay.
'used by' indicates a hidden word.
'ERSE' can be found hidden inside 'writers expressive'.
(Other definitions for erse that I've seen before include "Kind of Gaelic for seer" , "Old language spoken by strange seer" , "Irish Gaelic language" , "Name sometimes given to languages of the Celts in Ireland and Scotland" , "Old Scots or Irish Gaelic" .)