Practise children’s game with energy and fondness (6)
I believe the answer is:
dotage
'fondness' is the definition.
(thesaurus)
'practise children's game with energy' is the wordplay.
'practise' becomes 'do' ('do' can be a synonym of 'practise').
'children's game' becomes 'tag' (I've seen this before).
'with' is a charade indicator (letters next to each other).
'energy' becomes 'e' (physics symbol as in E=mc2).
'do'+'tag'+'e'='DOTAGE'
'and' is the link.
(Other definitions for dotage that I've seen before include "Senile years" , "when any activity may become difficult?" , "decrepitude" , "Second childhood" , "Old, weak period of life" .)