Hyperactive (5)
I believe the answer is:
manic
'hyperactive' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for manic that I've seen before include "Unnaturally excited" , "Showing wild excitement" , "Of mental state veering from depression to excitement" , "Ludicrously busy" , "Crazily excited" .)