That of jolly Roger, grinning away? (5)
I believe the answer is:
skull
If this is the answer I cannot explain how the clue works.
Can you help me to learn more?
(Other definitions for skull that I've seen before include "The head-bone" , "Bony frame of head ..." , "Cranium" , "brains here" , "Bony skeleton of the head" .)