Friend in church in Australia (5)
I believe the answer is:
china
'friend' is the definition.
(cockney rhyming slang, mate is china plate)
'in church in australia' is the wordplay.
'in' indicates a hidden word.
'CHINA' is hidden in the letters of 'church in australia'.
(Other definitions for china that I've seen before include "Porcelain; friend" , "Cathay was its archaic name" , "cup and saucer?" , "Household tableware" , "Country; friend (slang)" .)