Sadie's upset by such remarks (6)
I believe the answer is:
asides
'remarks' is the definition.
(I have seen 'Incidental remarks' mean 'asides' so perhaps 'remarks' could also mean 'asides')
'sadie's upset by' is the wordplay.
'upset by' is an anagram indicator.
'sadies' with letters rearranged gives 'ASIDES'.
'such' is the link.
(Other definitions for asides that I've seen before include "Stage-whispers" , "Stage whisper" , "Daises (anag.)" , "Stage whispers" , "Remarks not for overhearing" .)