Idler observing husband coming in after party (2,7)

'idler' is the definition.
(I know that idler can be written as do-nothing)

'observing husband coming in after party' is the wordplay.
'observing' becomes 'noting' ('note' can be a synonym of 'observe').
'husband' becomes 'h'.
'coming in' is an insertion indicator.
'after' says to put letters next to each other.
'party' becomes 'do' (do is a kind of party).
'noting' enclosing 'h' is 'nothing'.
'nothing' put after 'do' is 'DO-NOTHING'.