Coolest sort of cats! (7)
I believe the answer is:
ocelots
'cats' is the definition.
(ocelot is a kind of cat)
'coolest sort' is the wordplay.
'sort' indicates anagramming the letters.
'coolest' with letters rearranged gives 'OCELOTS'.
'of' acts as a link.
(Other definitions for ocelots that I've seen before include "Cats - cool set (anag)" , "Small leopards found in sole cot" , "Close to, oddly, the wildcats" , "animals in the wild" .)