In 'Major Barbara', an associate of royalty (3)
I believe the answer is:
orb
'royalty' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'in major barbara an associate' is the wordplay.
'in' indicates the answer is hidden within the clue.
'ORB' can be found hidden inside 'major barbara associate'.
'of' is the link.
Can you help me to learn more?
(Other definitions for orb that I've seen before include "Ring" , "Sphere - eye" , "Ornamental globe" , "Spherical symbol of monarch's power" , "Poetically eye" .)