What avoids circumlocution -- and is needed in tribunal, no end (7)
I believe the answer is:
candour
'what avoids circumlocution' is the definition.
'and is needed in tribunal no end' is the wordplay.
'is needed in' is an insertion indicator.
'tribunal' becomes 'court' ('court' can be a synonym of 'tribunal').
'no end' means to remove the last letter.
'court' with its final letter taken off is 'cour'.
'and' placed within 'cour' is 'CANDOUR'.
(Other definitions for candour that I've seen before include "Opening up" , "telling it like it is" , "'Frankness, honesty (7)'" , "sincerity" , "Frankness, openness" .)