___ penguin (7)
I believe the answer is:
emperor
'penguin' is the definition.
(emperor penguin is a kind of penguin)
This is the entire clue.
(Other definitions for emperor that I've seen before include "Beethoven piano concerto, Op. 73" , "Penguin of largest known species - a great ruler" , "Large richly coloured butterfly" , "A moth; a penguin" , "He rules over several states" .)