Song with spirit causes harm (6)
I believe the answer is:
impair
'harm' is the definition.
(I've seen this before)
'song with spirit' is the wordplay.
'song' becomes 'air' (I've seen this before).
'with' is a charade indicator (letters next to each other).
'spirit' becomes 'imp' (I have seen 'Evil spirit ' mean 'imp' so perhaps 'spirit' could also mean 'imp').
'air' put after 'imp' is 'IMPAIR'.
'causes' acts as a link.
(Other definitions for impair that I've seen before include "Spoil, degrade" , "Courteous man (colloq.)" , "Hinder" , "Hobble" , "Damage or injure" .)