Utterly enjoy Mad (4,5)
I believe the answer is:
like crazy
'utterly' is the definition.
Both the answer and definition are adverbs. Perhaps there's an association between them I don't understand?
'enjoy mad' is the wordplay.
'enjoy' becomes 'like' (like can mean to appreciate or enjoy something).
'mad' becomes 'crazy' (synonyms).
'like'+'crazy'='LIKE CRAZY'
Can you help me to learn more?
(Other definitions for like crazy that I've seen before include "great enthusiasm" , "Very much" , "Furiously" .)