Clergyman accepting a power plant (7)
I believe the answer is:
reactor
'power plant' is the definition.
(I've seen this before)
'clergyman accepting a' is the wordplay.
'clergyman' becomes 'rector' (rector is a kind of clergyman).
'accepting' means one lot of letters goes inside another (inserted letters are accepted).
'rector' going around 'a' is 'REACTOR'.
(Other definitions for reactor that I've seen before include "Nuclear energy source" , "Provider of nuclear power" , "Device to produce energy by nuclear fission" , "device that's energy-producing" , "Heart of a nuclear power station" .)