Mettlesome (8)
I believe the answer is:
spirited
'mettlesome' is the definition.
(I know that mettlesome can be written as spirited)
This is the entire clue.
(Other definitions for spirited that I've seen before include "Full of energy and enthusiasm" , "Full of beans" , "Sparkling" , "Lively, in upbeat mood" , "Mettlesome" .)