Notice god of the underworld will fail to hit man (9)
I believe the answer is:
dismissal
'notice' is the definition.
(I've seen this before)
'god of the underworld will fail to hit man' is the wordplay.
'god of the underworld' becomes 'dis' (I've seen this before).
'will' means one lot of letters go next to another (I've seen this in other clues).
'fail to hit' becomes 'miss' (I've seen this before).
'man' becomes 'al' (**).
'dis'+'miss'+'al'='DISMISSAL'
(Other definitions for dismissal that I've seen before include "Rejection" , "getting cards?" , "job loss?" , "sack" , "Termination of employment" .)