As drunk as this, went mad? (4)
I believe the answer is:
newt
'as drunk as this' is the definition.
(as in the phrase 'drunk as a newt')
'went mad?' is the wordplay.
'mad?' indicates an anagram (I've seen 'mad' mean this).
'went' anagrammed gives 'NEWT'.
(Other definitions for newt that I've seen before include "Amphibious creature" , "Pond creature" , "Went to find a sort of eft" , "animal" , "The epitome of drunkenness" .)