Old twit injecting drug spotted cat (6)
I believe the answer is:
ocelot
'spotted cat' is the definition.
'ocelot' can be an answer for 'cat' (ocelot is a kind of cat). I am not certain of the 'spotted' bit.
'old twit injecting drug' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'twit' becomes 'clot' (I can't explain this - if you can you should believe this answer much more).
'injecting' indicates putting letters inside.
'drug' becomes 'e' (e is another name for ecstasy).
'clot' enclosing 'e' is 'celot'.
'o'+'celot'='OCELOT'
Can you help me to learn more?
(Other definitions for ocelot that I've seen before include "Fur" , "Wildcat -- loo etc (anag)" , "Wild cat, native to Central and South America - loo etc (anag)" , "Wild cat of the Americas" , "Spotted New World feline" .)