His E-mail has a letter missing (4)
I believe the answer is:
emil
'his' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'e-mail has a letter missing' is the wordplay.
'e-mail has' becomes 'e' (I can't explain this - if you can you should believe this answer much more).
'letter' becomes 'mail'.
'missing' indicates named letters should be taken away.
'mail' with 'a' taken out is 'mil'.
'e'+'mil'='EMIL'
Can you help me to learn more?
(Other definitions for emil that I've seen before include "- - Zatopek, Olympic runner" , "French boy's name" , "German boy" .)