Completely unknown priest turning up in a German church (5,4)
I believe the answer is:
every inch
'completely' is the definition.
(synonyms)
'unknown priest turning up in a german church' is the wordplay.
I cannot quite understand how this works, but
'unknown' could be 'y' (algebra) and 'y' is located in the answer.
'in' is found in the answer.
'church' could be 'rc' (abbreviation for Roman Catholic) and 'rc' is present in the remaining letters.
This explanation may well be incorrect...
(Other definitions for every inch that I've seen before include "Wholly" , "Entirely" , "In all departments" , "Thoroughly" , "completely" .)