Lively quote half-hearted author's written up (9)
I believe the answer is:
energetic
'lively' is the definition.
(similar in meaning)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for energetic that I've seen before include "Forceful and with great vitality" , "High-powered" , "Vigorous and dynamic" , "Showing great activity" , "It's vital" .)