Place to sit on high in a church (5)
I believe the answer is:
perch
'place to sit on high' is the definition.
(an elevated seat)
'a church' is the wordplay.
'a' becomes 'per'.
'church' becomes 'ch' (common abbreviation).
'per'+'ch'='PERCH'
'in' is the link.
(Other definitions for perch that I've seen before include "Fish; pole" , "Resting place for a bird and old measure" , "What angler may catch" , "(Fishy) pole where bird sits" , "A fish; alighting place" .)