Muppet drummer, I'm upset with Lana (6)
I believe the answer is:
animal
'muppet drummer' is the definition.
(I've seen this in another clue)
'i'm upset with lana' is the wordplay.
'upset with' indicates anagramming the letters.
'im' with its letters mixed up with 'lana' gives 'ANIMAL'.
(Other definitions for animal that I've seen before include "Circus performer, maybe" , "Creature having voluntary movement" , "Beastly" , "One sharing our kingdom" , "Mammal" .)