Policeman shows sign of nerves in church (6)
I believe the answer is:
coptic
'church' is the definition.
(Coptic Church is an example)
'policeman shows sign of nerves' is the wordplay.
I cannot really understand how this works, but
'policeman' could be 'cop' (slang term) and 'cop' is found in the answer.
'sign of nerves' could be 'tic' (as in a nervous tic) and 'tic' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'in' acts as a link.
Can you help me to learn more?
(Other definitions for coptic that I've seen before include "religious language" , "Sweet; fungus" , "Orthodox Christian church based in Egypt" , "Ancient church language" , "Egyptians in the past" .)