Crazy drinking energy drink (4)
I believe the answer is:
mead
'drink' is the definition.
(mead is a kind of drink)
'crazy drinking energy' is the wordplay.
'crazy' becomes 'mad' (synonyms).
'drinking' is an insertion indicator (inserted letters are consumed or drunk).
'energy' becomes 'e' (physics symbol as in E=mc2).
'mad' enclosing 'e' is 'MEAD'.
(Other definitions for mead that I've seen before include "Old honey-based drink for dame" , "Honeyed drink for dame" , "Honey drink; lea" , "Drink made of fermented honey and water" , "Alcoholic drink of fermented honey and water of old" .)