Morph noticing nothing, unnoticed? (9)
I believe the answer is:
incognito
'unnoticed?' is the definition.
(incognito means in disguise or undetected)
'morph noticing nothing' is the wordplay.
'morph' indicates an anagram (the letters morph into a new form).
'nothing' becomes 'o' (looks like zero - 0).
'noticing' with letters rearranged gives 'incognit'.
'incognit'+'o'='INCOGNITO'
(Other definitions for incognito that I've seen before include "Anonymously" , "under another name" , "hiding identity" , "Under an assumed name" , "In disguise" .)