Slander when being about individual (9)
I believe the answer is:
aspersion
'slander' is the definition.
(synonyms)
'when being about individual' is the wordplay.
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'being' becomes 'person' (person is a kind of being).
'about' is an insertion indicator.
'individual' becomes 'i' (Roman numeral for one).
'person' going around 'i' is 'persion'.
'as'+'persion'='ASPERSION'
(Other definitions for aspersion that I've seen before include "Cast this slur" , "Malicious remark" , "Defamatory suggestion" , "Slander" , "reflection" .)