Language in truer sentence (4)
I believe the answer is:
erse
'language' is the definition.
(Erse is an example)
'in truer sentence' is the wordplay.
'in' says the answer is hidden in the clue.
'ERSE' is hidden in the letters of 'truer sentence'.
(Other definitions for erse that I've seen before include "Possibly the language" , "Old Scots or Irish Gaelic" , "Old name for Celtic languages" , "Kind of Gaelic for seer" , "Irish Gaelic language" .)