Encounter abrupt professional upsetting niece (10)
I believe the answer is:
experience
'encounter' is the definition.
(I know that encounter is a kind of experience)
'abrupt professional upsetting niece' is the wordplay.
I cannot quite see how this works, but
an anagram of 'niece' is 'ience' which is within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for experience that I've seen before include "Encounter" , "Undergo" , "what Hendrix had" , "Participate in - knowledge and understanding gained" , "Witness" .)