Article about boxing is true to life (9)
I believe the answer is:
realistic
'true to life' is the definition.
(similar in meaning)
'article about boxing is' is the wordplay.
'about' indicates anagramming the letters.
'boxing' is an insertion indicator ('box' can mean contain, as in to put in a box).
'article' anagrammed gives 'realtic'.
'realtic' placed around 'is' is 'REALISTIC'.
(Other definitions for realistic that I've seen before include "Level-headed" , "Without illusions, dealing in facts" , "Objective" , "Practicable" , "Down-to-earth" .)