Study part of church plan (8)
I believe the answer is:
conspire
'plan' is the definition.
(I've seen this before)
'study part of church' is the wordplay.
'study' becomes 'con' (I've seen this before).
'part of church' becomes 'spire'.
'con'+'spire'='CONSPIRE'
(Other definitions for conspire that I've seen before include "Act secretly with others" , "Plot secretly" , "So prince is given to plan secretly with others" , "Secretly plan together" , "Collude" .)