Upset seeing husband in public squabble (9)
I believe the answer is:
overthrow
'upset' is the definition.
('overthrow' can be a synonym of 'upset')
'husband in public squabble' is the wordplay.
'husband' becomes 'h'.
'in' means one lot of letters goes inside another.
'public' becomes 'overt' ('overt' is associated in meaning with 'public').
'squabble' becomes 'row' (I've seen this in other clues).
'overt'+'row'='overtrow'
'h' placed within 'overtrow' is 'OVERTHROW'.
'seeing' is the link.
(Other definitions for overthrow that I've seen before include "depose government" , "destruction" , "caused discomfiture" , "Unseat" , "Fall" .)