Whatever the grammatical classification of these words though, "ghjattu-volpe" (like French "chat-renard") would clearly be translated as "fox-cat" into English. In both cases, even though "fox" might not be technically an adjective, it's functionally a mere modifier for "cat".
Gatto volpe in Italian would be best translated as fox cat.
Italian speakers often kind of mangle English pairs that way in that they'll drop the second word, like "Pulled Pork" becoming "Il Pulled" in an online group about BBQ I used to subscribe too.