Highly curious (4)
I believe the answer is:
agog
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">highly curious</span>' is the definition.<br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for agog that I've seen before include "All ears" , "Wide-eyed and fascinated" , "In excited eagerness" , "Expecting" , "Eager or curious" .)