Notice nothing causing fuss (3)
I believe the answer is:
ado
'fuss' is the definition.
(synonyms)
'notice nothing' is the wordplay.
'notice' becomes 'ad' (short for advert).
'nothing' becomes 'o' (looks like zero - 0).
'ad'+'o'='ADO'
'causing' acts as a link.
(Other definitions for ado that I've seen before include "excitement" , "Song and dance" , "Fuss or bustle" , "stir" , "agitation" .)