Resentful, dining out with worker (9)
I believe the answer is:
indignant
'resentful' is the definition.
(thesaurus)
'dining out with worker' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'with' says to put letters next to each other.
'worker' becomes 'ant' (worker is a type of ant).
'dining' anagrammed gives 'indign'.
'indign'+'ant'='INDIGNANT'
(Other definitions for indignant that I've seen before include "not happy" , "Anger at having been treated unjustly" , "feeling anger" , "Up in arms" , "Somewhat outraged" .)