What you might be called by posh types (3)
I believe the answer is:
one
'be called by posh types' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for one that I've seen before include "I can mean this" , "Hour after midnight" , "both halves" , "Single and undivided" , "This is singular" .)