As insane with great energy (4,3)
I believe the answer is:
like mad
'great energy' is the definition.
The answer and definition are not the same part of speech.
'as insane' is the wordplay.
'as' becomes 'like' (I've seen this in other clues).
'insane' becomes 'mad' (synonyms).
'like'+'mad'='LIKE MAD'
'with' is the link.
Can you help me to learn more?
(Other definitions for like mad that I've seen before include "Energetically" , "wildly" , "With great intensity, energy, or enthusiasm" , "Very quickly" , "Furiously" .)