Bad-tempered? More so, unfortunately (6)
I believe the answer is:
morose
'bad-tempered?' is the definition.
(morose means sad or in a bad mood)
'more so unfortunately' is the wordplay.
'unfortunately' indicates anagramming the letters (a bad or unfortunate spelling).
'more'+'so'='moreso'
'moreso' is an anagram of 'MOROSE'.
(Other definitions for morose that I've seen before include "Sullen. bad-tempered" , "Lugubrious" , "in gloomy mood" , "Sad" , "Gloomy and unsociable" .)