British church takes one in their arm (6)
I believe the answer is:
branch
'arm' is the definition.
(synonyms)
'british church takes one in' is the wordplay.
'british' becomes 'br'.
'church' becomes 'ch' (common abbreviation).
'takes' means one lot of letters go next to another.
'one' becomes 'an' ('a' and 'an' can mean 'one').
'in' indicates putting letters inside.
'br'+'ch'='brch'
'brch' enclosing 'an' is 'BRANCH'.
'their' is the link.
This may not be correct. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for branch that I've seen before include "regional office" , "division within large organisation" , "Part of a tree; division" , "Part of tree/river" , "Trunk offshoot" .)