Ado with eldest abused, made very unhappy (9)
I believe the answer is:
desolated
'very unhappy' is the definition.
(desolated means very upset)
'ado with eldest abused' is the wordplay.
'with' means one lot of letters go next to another.
'abused' indicates anagramming the letters.
'ado' put after 'eldest' is 'eldestado'.
'eldestado' with letters rearranged gives 'DESOLATED'.
'made' acts as a link.
(Other definitions for desolated that I've seen before include "Feeling lonely and wretched" , "Made extremely sad" , "Abandoned, ruined" .)