### Clue: The first to complain after priest hides copy of evidence of activity (5,5)
### Answer: PAPER TRAIL 
 ### Explanation: Definition: evidence of activity
 **The 1st letter of**(… first) "The" + RAIL(to complain bitterly or vehemently) **placed after**(after) [ PR(abbrev. for "priest") **containing**(hides) APE(to copy) ].