Disregard Italian gentleman losing head (6)
I believe the answer is:
Here is my best explanation:
'disregard' is the definition.
('ignore' can be a synonym of 'disregard')
'italian gentleman losing head' is the subsidiary indication.
'italian gentleman' becomes 'signore'.
'losing head' means to remove the first letter.
'signore' with its first letter taken away is 'ignore'.
(Other definitions for ignore that I've seen before include "Walk away from", "Snub", "bypass", "Deliberately overlook", "Forget", "'Disregard, overlook (6)'", "Cut, disregard", "Region in which to snub", "Region (anag)" and "Deliberately disregard".)