Organ; bad temper (6)
I believe the answer is:
spleen
I believe this clue is a double definition.
'organ' is the first definition.
(the spleen is an organ)
'bad temper' is the second definition.
(informal term for bad temper)
(Other definitions for spleen that I've seen before include "Acrimony" , "Bodily organ associated with bad temper" , "Organ of the body - ill temper" , "The organ once thought to be the seat of anger" , "Human organ" .)