Not entirely relevant language (6)
I believe the answer is:
german
'language' is the definition.
(German is an example)
'not entirely relevant' is the wordplay.
'not entirely' means to remove the last letter.
'relevant' becomes 'germane' (similar in meaning).
'germane' with its final letter removed is 'GERMAN'.
(Other definitions for german that I've seen before include "Middle European, for example" , "Teutonic language" , "Alsatian" , "European language" , "Goethe's language" .)