Leave church key in bishop's office (6)
I believe the answer is:
secede
'leave' is the definition.
(I've seen this in another clue)
'church key in bishop's office' is the wordplay.
'church' becomes 'CE' (abbreviation for Church of England).
'key' becomes 'd' (musical key).
'in' indicates putting letters inside.
'bishop's office' becomes 'see' (I've seen this before).
'ce'+'d'='ced'
'ced' placed into 'see' is 'SECEDE'.
(Other definitions for secede that I've seen before include "Make a formal withdrawal" , "leave union" , "Withdraw from, say organisation" , "Withdraw (from a federal union or organisation)" , "Formally achieve independence" .)