Emotional reaction shown by rich state in transition (9)
I believe the answer is:
theatrics
'emotional reaction' is the definition.
'shown by rich state in transition' is the wordplay.
'shown by' means one lot of letters go next to another.
'in transition' is an anagram indicator.
'rich'+'state' is 'richstate'.
'richstate' is an anagram of 'THEATRICS'.
(Other definitions for theatrics that I've seen before include "Histrionics" , "dramatic outburst" .)