Old idiot - taking in oriental cat! (6)
I believe the answer is:
'cat' is the definition.
(ocelot is a kind of cat)
'old idiot taking in oriental' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'idiot' becomes 'clot' (I've seen this in other clues**).
'taking in' indicates putting letters inside.
'oriental' becomes 'e'.
'clot' enclosing 'e' is 'celot'.
(Other definitions for ocelot that I've seen before include "Send animal to Cole" , "Wild cat, native to Central and South America - loo etc (anag)" , "Leopard-like cat of S America" , "Type of American wildcat" , "South and Central American wildcat" .)