Anger that is about right (3)
I believe the answer is:
ire
'anger' is the definition.
(ire is intense rage)
'that is about right' is the wordplay.
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'about' means one lot of letters goes inside another.
'right' becomes 'r' (common abbreviation).
'ie' placed around 'r' is 'IRE'.
(Other definitions for ire that I've seen before include "Irritation, anger" , "Anger, rage" , "Displeasure" , "passion" , "Paddy" .)