One king flanked by others in church (4)
I believe the answer is:
kirk
'church' is the definition.
(kirk is a Scottish term for a church)
'one king flanked by others' is the wordplay.
'one' becomes 'i' (Roman numeral).
'king' becomes 'R' (abbreviation for rex, king in Latin).
'flanked by' means one lot of letters goes inside another (other letters go on other side).
'others' becomes 'kk' (I can't explain this - if you can you should believe this answer much more).
'i'+'r'='ir'
'ir' put into 'kk' is 'KIRK'.
'in' acts as a link.
(Other definitions for kirk that I've seen before include "Church of Scotland" , "Scots church" , "Presbyterian building?" , "Star Trek captain - Scottish church" .)