Old Egyptian policeman gets a twitch (6)
I believe the answer is:
coptic
'old egyptian' is the definition.
'Coptic' can be an answer for 'egyptian' (Coptic is an example). I am unsure of the 'old' bit.
'policeman gets a twitch' is the wordplay.
'policeman' becomes 'cop' (slang term).
'gets' says to put letters next to each other.
'a twitch' becomes 'tic' (tic is a kind of twitch).
'cop'+'tic'='COPTIC'
Can you help me to learn more?
(Other definitions for coptic that I've seen before include "religious language" , "Ancient Christian church of Egypt" , "Sweet; fungus" , "Orthodox Christian church based in Egypt" , "Ancient church language" .)