Disregard Italian gentleman losing head (6)
I believe the answer is:
ignore
'disregard' is the definition.
('ignore' can be a synonym of 'disregard')
'italian gentleman losing head' is the wordplay.
'italian gentleman' becomes 'signore'.
'losing head' means to remove the first letter.
'signore' with its initial letter removed is 'IGNORE'.
(Other definitions for ignore that I've seen before include "Refuse to notice or acknowledge" , "Intentionally disregard" , "Walk away from" , "Blank" , "Give no attention to" .)