Drunken mingler is troublemaker (7)
I believe the answer is:
gremlin
'is troublemaker' is the definition.
(I've seen this in another clue)
'drunken mingler' is the wordplay.
'drunken' indicates an anagram.
'mingler' is an anagram of 'GREMLIN'.
(Other definitions for gremlin that I've seen before include "Impish troublemaker" , "Cause of unexpected mechanical problem" , "Fault-causing sprite" , "Technical bug" , "Mechanical fault" .)