Minor act of neglect (6)
I believe the answer is:
slight
This clue is a triple definition!
'minor' is the first definition.
(I've seen this before)
'act' is the second definition.
(slight is a kind of act)
'of' acts as a link.
'neglect' is the third definition.
(synonyms)
(Other definitions for slight that I've seen before include "Disregard - snub" , "Insignificant, flimsy" , "Slim or tenuous" , "of no great significance" , "Affront of delicate sort" .)