Ignore Diana's affection (9)
I believe the answer is:
disregard
'ignore' is the definition.
(synonyms)
'diana's affection' is the wordplay.
'diana's' becomes 'Di's' (Di is short for Diana).
'affection' becomes 'regard' (regard is a kind of affection).
'dis'+'regard'='DISREGARD'
(Other definitions for disregard that I've seen before include "Push aside" , "Neglect, ignore" , "Overlook - inattention" .)