One event with barristers concerning chambers (6)
I believe the answer is:
atrial
'one event with barristers concerning chambers' is the definition.
I can't tell whether this definition defines the answer.
'one event with barristers concerning' is the wordplay.
'one event' becomes 'trial' (trial is a kind of event).
'with' says to put letters next to each other.
'barristers concerning' becomes 'a' (I am not sure about this - if you are sure you should believe this answer much more).
'trial' after 'a' is 'ATRIAL'.
Can you help me to learn more?
(Other definitions for atrial that I've seen before include "Like some courts" , "Lariat (anag)" , "referring to Chambers?" , "of the heart cavities" , "Like main court" .)