Keen, enthusiastic (5)
I believe the answer is:
eager
I believe this is a double definition.
'keen' is the first definition.
(I've seen this before)
'enthusiastic' is the second definition.
(similar in meaning)
(Other definitions for eager that I've seen before include "It's a bore" , "Agree (anag.)" , "Keen, avid" , "Keen (as a beaver?)" , "Enthusiastic, raring to go" .)