Worried seeing sweet son upset (8)
I believe the answer is:
stressed
'worried' is the definition.
'sweet son upset' is the wordplay.
'sweet' becomes 'dessert' (synonyms).
'son' becomes 's' (genealogical abbreviation for son).
'upset' says the letters should be written in reverse.
'dessert'+'s'='desserts'
'desserts' reversed gives 'STRESSED'.
'seeing' is the link.
(Other definitions for stressed that I've seen before include "Hassled, under pressure" , "Suffering from physical or emotional strain" , "Strained or emphasised" , "Emphasized or strained" , "Under great strain" .)