Deer essentially bit tongue (5)
I believe the answer is:
hindi
'tongue' is the definition.
(Hindi is an example)
'deer essentially bit' is the wordplay.
'deer' becomes 'hind' (hind is a kind of deer).
'essentially' says to take the centre.
The centre of 'bit' is 'i'.
'hind'+'i'='HINDI'
(Other definitions for hindi that I've seen before include "One of India's official languages" , "Ind. Language" , "tongue" , "Language of northern India" , "Language derived from Sanskrit" .)