Prohibiting new red bra leads to, invariably, no good (9)

'prohibiting' is the definition.
(debarring is a kind of prohibiting)

'new red bra leads to invariably no good' is the wordplay.
'new' indicates anagramming the letters.
'leads to' says to take the initial letters.
The first letters of 'invariably no good' is 'ing'.
'red'+'bra'='redbra'
'redbra' anagrammed gives 'debarr'.
'debarr'+'ing'='DEBARRING'