Dismiss what’s upsetting to us (4)
I believe the answer is:
oust
'dismiss' is the definition.
(thesaurus)
'upsetting to us' is the wordplay.
'upsetting' indicates an anagram.
'to'+'us'='tous'
'tous' is an anagram of 'OUST'.
'what's' acts as a link.
(Other definitions for oust that I've seen before include "Remove and replace" , "Extract" , "Show the door to" , "Drive out, expel" , "Expel - eject" .)