Naughty Adam's a charmer -- ah, terribly, terribly crazy! (3,2,1,5,4)
I believe the answer is:
mad as a march hare
'terribly crazy' is the definition.
(as mad as a march hare means very mad)
'naughty adam's a charmer ah terribly' is the wordplay.
'naughty' indicates anagramming the letters.
'terribly' indicates anagramming the letters.
'adams' is an anagram of 'madas'.
'charmer'+'ah'='charmerah'
'charmerah' with letters rearranged gives 'marchhare'.
'madas'+'a'+'marchhare'='MAD AS A MARCH HARE'
(Other definitions for mad as a march hare that I've seen before include "like a Tea Party member?" , "Crazy" , "Unstable" , "Out to lunch" , "Behaving excitably and unpredictably (3,2,1,5,4)" .)