A man in charge joins mansion and reactor (6,4)

I believe the answer is:

atomic pile

'reactor' is the definition.
(atomic pile is a kind of reactor)

'a man in charge joins mansion' is the wordplay.
'man' becomes 'tom' (man's name).
'in charge' becomes 'ic' (abbreviation for 'in charge').
'joins' is a charade indicator (letters next to each other).
'mansion' becomes 'pile' (pile can mean a large building).
'a'+'tom'+'ic'+'pile'='ATOMIC PILE'

'and' acts as a link.

(Another definition for atomic pile that I've seen is " Old name for nuclear reactor".)

I've seen this clue in The Daily Express.

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