Great enthusiasm and energy (4)
I believe the answer is:
zest
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">great enthusiasm and energy</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for zest that I've seen before include "extract of lemon?" , "Joie de vivre" , "Drive" , "Zeal" , "Orange or lemon peel" .)