Note merger after company disorder (9)
I believe the answer is:
confusion
'disorder' is the definition.
(I know that confusion is a type of disorder)
'note merger after company' is the wordplay.
'note' becomes 'n' (abbreviation).
'merger' becomes 'fusion' (synonyms).
'after' is a charade indicator (letters next to each other).
'company' becomes 'co' (abbreviation).
'n'+'fusion'='nfusion'
'nfusion' after 'co' is 'CONFUSION'.
(Other definitions for confusion that I've seen before include "Chaos" , "Shame!" , "Bewilderment - disorder" , "Perplexity" , "Uncertainty" .)