Pet at Macy’s running with tip of leash causing disaster (9)
I believe the answer is:
cataclysm
'disaster' is the definition.
(synonyms)
'pet at macy's running with tip of leash' is the wordplay.
'pet' becomes 'cat' (cats are often kept as pets).
'at' is a charade indicator (letters next to each other).
'running with' is an anagram indicator.
'tip of' says to take the initial letters.
The initial letter of 'leash' is 'l'.
'macys' mixed up with 'l' gives 'aclysm'.
'cat'+'aclysm'='CATACLYSM'
'causing' is the link.
(Other definitions for cataclysm that I've seen before include "Deluge: upheaval" , "A clam cyst could be a disaster" , "Sudden violent change in the earth's surface" , "Calamity" , "Disastrous upheaval or flood" .)