Half of nuclear power plant includes electron capture (5)
I believe the answer is:
seize
'capture' is the definition.
(I know that capture can be written as seize)
'half of nuclear power plant includes electron' is the wordplay.
'half of' suggests halving the letters.
'nuclear power plant' becomes 'Sizewell' (British nuclear power station).
'includes' is an insertion indicator.
'electron' becomes 'e' (abbreviation in physics).
'sizewell' cut in half is 'size'.
'size' enclosing 'e' is 'SEIZE'.
(Other definitions for seize that I've seen before include "appropriate" , "square in Paris" , "Snatch" , "Take by force" , "Grasp forcibly" .)