Time to change mail's language (5)
I believe the answer is:
tamil
'language' is the definition.
(Tamil is an example)
'time to change mail's' is the wordplay.
'time' becomes 't' (abbreviation).
'to change' indicates an anagram.
'mail' is an anagram of 'amil'.
't'+'amil'='TAMIL'
(Other definitions for tamil that I've seen before include "One in race" , "Perhaps Indian" , "Native of south India or Sri Lanka" , "S. India/Sri Lankan person, tongue" , "An official language of Sri Lanka" .)