Permit 51 churches to keep name (7)
I believe the answer is:
licence
'permit' is the definition.
(I know that permit can be written as licence)
'51 churches to keep name' is the wordplay.
'5c' becomes 'LI' (roman numeral).
'churches' becomes 'cece' (I can't justify this - if you can you should believe this answer much more).
'to keep' means one lot of letters goes inside another.
'name' becomes 'n' (common abbreviation e.g. on forms).
'cece' placed around 'n' is 'cence'.
'li'+'cence'='LICENCE'
Can you help me to learn more?
(Other definitions for licence that I've seen before include "Formal permit" , "-- plate; poetic --" , "Official permit" , "Self-indulgence; permit" , "Permit - freedom" .)