Believe part of play about church power (6)
I believe the answer is:
accept
'believe' is the definition.
(I've seen this before)
'play about church power' is the wordplay.
'play' becomes 'act' (synonyms).
'about' means one lot of letters goes inside another.
'church' becomes 'ce' (Church of England).
'power' becomes 'p' (symbol in physics).
'ce'+'p'='cep'
'act' enclosing 'cep' is 'ACCEPT'.
'part of' acts as a link.
(Other definitions for accept that I've seen before include "Take on; tolerate" , "Receive voluntarily" , "Believe to be correct; take on" , "agree to buy" , "Take as a gift" .)