Diana's failed to make a hit - sacked (9)
I believe the answer is:
dismissed
'sacked' is the definition.
('dismiss' can be a synonym of 'sack')
'diana's failed' is the wordplay.
'diana's' becomes 'Di's' (Di is short for Diana).
'failed' becomes 'missed' (missing is a kind of failing).
'dis'+'missed'='DISMISSED'
'to make a hit' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for dismissed that I've seen before include "put out of court" , "Spurned" , "Fired" , "Brushed off or sacked" .)