Enthusiastic, and sharp, too
I believe the answer is:
keen
'enthusiastic' is the definition.
(I've seen this in another clue)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for keen that I've seen before include "Eager; wail in grief" , "moan" , "display grief" , "Itching" , "Avid, enthusiastic" .)