United go over stopping time to attack — it’s not going to work (5,3)

'not going to work' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.

'united go over stopping time to attack' is the wordplay.
'united' becomes 'U' (as in Man U, Manchester United).
'go over' becomes 'vet' (vetting is a kind of going over).
'stopping' means one lot of letters goes inside another (stopping can mean blocking a gap).
'time to attack' becomes 'd-day' (I've seen this in another clue).
'u'+'vet'='uvet'
'uvet' inserted into 'dday' is 'DUVET DAY'.

'it's' acts as a link.

Can you help me to learn more?