Norma is about to describe capital (5)
I believe the answer is:
roman
'capital' is the definition.
(thesaurus)
'norma is about' is the wordplay.
'is about' indicates an anagram.
'norma' with letters rearranged gives 'ROMAN'.
'to describe' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for roman that I've seen before include "Our alphabet; upright type" , "Denizen of Italian capital" , "French story" , "Audrey Hepburn film (time off in Italy)" , "Upright form of type" .)