Showed bad spirit having started badly (12)
I believe the answer is:
demonstrated
'showed' is the definition.
(demonstrating is a kind of showing)
'bad spirit having started badly' is the wordplay.
'bad spirit' becomes 'demon' (I've seen this before).
'having' is a charade indicator (letters next to each other).
'badly' is an anagram indicator (letters in the wrong order).
'started' anagrammed gives 'strated'.
'demon'+'strated'='DEMONSTRATED'
(Other definitions for demonstrated that I've seen before include "shown up" , "made public protest" .)