Copy a lion (4)
I believe the answer is:
roar
'copy a lion' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for roar that I've seen before include "Shout loudly" , "24 [BOOM]" , "cheer" , "Lion's sound" , "The __ of the Greasepaint -- The Smell of the Crowd (1964 musical)" .)