Mum may see son fast after Italy (6)
I believe the answer is:
silent
'mum' is the definition.
('silent' can be a synonym of 'mum')
'son fast after italy' is the wordplay.
'son' becomes 's'.
'fast' becomes 'lent' (I've seen this before).
'after' means one lot of letters go next to another.
'italy' becomes 'i'.
'lent' after 'i' is 'ilent'.
's'+'ilent'='SILENT'
'may see' acts as a link.
(Other definitions for silent that I've seen before include "Taciturn" , "Soundless" , "Unheard" , "the moderate majority?" , "Strange and astonishing thing" .)