Willing to admit nothing after the atom disintegrated (2,4,2)

'willing to admit' is the definition.
(as in being at home to guests)

'nothing after the atom disintegrated' is the wordplay.
'nothing' becomes 'O' (O resembles 0).
'after' says to put letters next to each other.
'disintegrated' indicates an anagram.
'the'+'atom'='theatom'
'theatom' is an anagram of 'athomet'.
'o' put after 'athomet' is 'AT HOME TO'.