Like the king of the jungle (7)
I believe the answer is:
'like the king of the jungle' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for leonine that I've seen before include "Catty" , "Like the king of the beasts" , "about a big beast" , "Like a wild animal" , "It's like Aslan" .)