Tedious fight curtailed by fight venue (6)
I believe the answer is:
boring
'tedious' is the definition.
(synonyms)
'fight curtailed by fight venue' is the wordplay.
'fight' becomes 'box' (boxing is a kind of fighting).
'curtailed' means to remove the last letter.
'by fight venue' becomes 'ring' (I am not sure about this - if you are sure you should believe this answer much more).
'box' with its last letter removed is 'bo'.
'bo'+'ring'='BORING'
Can you help me to learn more?
(Other definitions for boring that I've seen before include "Tedious and tiring" , "Mentally wearying" , "Making holes" , "Drilling can be tedious" , "Drilling - it's monotonous" .)