Very happy, giddy teens online, tackling me (2,4,7)
I believe the answer is:
in ones element
'very happy' is the definition.
'giddy teens online tackling me' is the wordplay.
'giddy' indicates anagramming the letters.
'tackling' indicates putting letters inside (I've seen this in other clues).
'teens'+'online'='teensonline'
'teensonline' with letters rearranged gives 'inoneselent'.
'inoneselent' going around 'me' is 'IN ONES ELEMENT'.
(Other definitions for in ones element that I've seen before include "Involved in naturally suited sphere" , "Within a pleasing environment" , "Occupied with something that gives great pleasure" .)