Old fool keeps electronic cat (6)
I believe the answer is:
ocelot
'cat' is the definition.
(I know that ocelot is a type of wildcat)
'old fool keeps electronic' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'fool' becomes 'clot' (I've seen this before).
'keeps' means one lot of letters goes inside another.
'electronic' becomes 'e' (as in e-mail or e-books).
'clot' enclosing 'e' is 'celot'.
'o'+'celot'='OCELOT'
(Other definitions for ocelot that I've seen before include "Wild cat, native to Central and South America - loo etc (anag)" , "Striped and spotted wildcat" , "Wildcat -- loo etc (anag)" , "Small leopardlike cat" , "Send animal to Cole" .)