Jargon used in emailing others (5)
I believe the answer is:
lingo
'jargon' is the definition.
('lingo' can be a synonym of 'jargon')
'in emailing others' is the wordplay.
'in' says the answer is hidden in the clue.
'LINGO' is hidden in the letters of 'emailing others'.
'used' is the link.
(Other definitions for lingo that I've seen before include "Log in (anag.)" , "Jargon, foreign language (informal)" , "Jargon, language (colloq.)" , "Patois" , "Language (slang)" .)