Old fool importing European wildcat (6)
I believe the answer is:
ocelot
'wildcat' is the definition.
(ocelot is a kind of wildcat)
'old fool importing european' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'fool' becomes 'clot' (I've seen this before).
'importing' indicates putting letters inside.
'european' becomes 'e' (abbreviation e.g. EU).
'clot' going around 'e' is 'celot'.
'o'+'celot'='OCELOT'
(Other definitions for ocelot that I've seen before include "Nocturnal wild cat of Central and South America" , "Feline of South and Central America" , "Type of American wildcat" , "Wild cat of the Americas" , "American cat, like a small leopard" .)