Clue: Creature half-ugly eaten by one of Lear's (6)
Answer: DUGONG
Explanation: Creature half-ugly eaten by one of Lear's (6)

[*half-*] **UG**(ly) *eaten by* **DONG** ("one of Lear's (creatures)")
 

 
*A dugong is a marine mammal, related to the manatee, and Edward Lear's Dong was famous for its bright nose.*
 

 
*"The Dong! — the Dong!*
 
*"The wandering Dong through the forest goes!*
 
*"The Dong! the Dong!*
 
*"The Dong with a luminous Nose!"