Clergyman in church by a prairie (8)
I believe the answer is:
chaplain
'clergyman' is the definition.
(chaplain is a kind of clergyman)
'church by a prairie' is the wordplay.
'church' becomes 'ch' (common abbreviation).
'by' means one lot of letters go next to another.
'prairie' becomes 'plain'.
'ch'+'a'+'plain'='CHAPLAIN'
'in' is the link.
(Other definitions for chaplain that I've seen before include "Member of the clergy attached to an institution" , "cleric" , "Army padre" , "Member of clergy ministering to an organisation" , "Member of the clergy, in 24 ac say" .)