Welcome little new for traditional occasion (9)
I believe the answer is:
halloween
'traditional occasion' is the definition.
'welcome little new' is the wordplay.
'welcome' becomes 'hallo' (both are greetings).
'little' becomes 'wee' (similar in meaning).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'hallo'+'wee'+'n'='HALLOWEEN'
'for' is the link.
(Other definitions for halloween that I've seen before include "Evening of masquerade" , "31st October" , "movie with many cuts" , "annual celebration" , "Night of October thirty-first" .)