Old Cicero's untidy file (9)
I believe the answer is:
crocodile
'file' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'old cicero's untidy' is the wordplay.
'untidy' indicates anagramming the letters.
'old'+'cicero'='oldcicero'
'oldcicero' is an anagram of 'CROCODILE'.
Can you help me to learn more?
(Other definitions for crocodile that I've seen before include "handbag material?" , "Large aquatic reptile" , "Procession of schoolchildren" , "Tropical reptile" , "Line of children walking in twos" .)