Hen and rat running wild round extreme characters in pilgrimage centre (8)
I believe the answer is:
nazareth
'pilgrimage centre' is the definition.
(destination for Christian pilgrimages)
'hen and rat running wild round extreme characters' is the wordplay.
'and' is a charade indicator (letters next to each other).
'running wild' indicates anagramming the letters.
'round' means one lot of letters goes inside another.
'extreme characters' becomes 'AZ' (letters at the extremes of the alphabet).
'hen' put after 'rat' is 'rathen'.
'rathen' with letters rearranged gives 'nareth'.
'nareth' going around 'az' is 'NAZARETH'.
'in' is the link.
(Other definitions for nazareth that I've seen before include "Town where Jesus grew up" , "According to the Gospels, Jesus grew up here" , "where preacher was raised" , "Town where Jesus spent his youth" , "Town where Jesus was reared" .)