Note the Italian's collapse (4)
I believe the answer is:
fail
'collapse' is the definition.
(I've seen this before)
'note the italian's' is the wordplay.
'note' becomes 'fa' (fourth note in sol-fa notation: doh, ray, me...).
'the italian' becomes 'il' ('the' in Italian).
'fa'+'il'='FAIL'
(Other definitions for fail that I've seen before include "Stop working properly" , "Go wrong" , "Go bankrupt" , "Fall short" , "Be unsuccessful, say in exam" .)