Withdraw notice involving church close to Oxford (6)
I believe the answer is:
secede
'withdraw' is the definition.
(I've seen this before)
'notice involving church close to oxford' is the wordplay.
'notice' becomes 'see' (I've seen this before).
'involving' is an insertion indicator.
'church' becomes 'ce' (abbreviation for Church of England).
'close to' says to take the final letters (the close/ending of).
The final letter of 'oxford' is 'd'.
'ce'+'d'='ced'
'see' going around 'ced' is 'SECEDE'.
(Other definitions for secede that I've seen before include "Withdraw formally from membership of an organisation" , "Withdraw (from organization)" , "Formally achieve independence" , "Withdraw from a body, a nation say" , "Make a formal withdrawal" .)