Obstacle race half lost amid tennis tournament (6)
I believe the answer is:
slalom
'obstacle race' is the definition.
(I've seen this before)
'half lost amid tennis tournament' is the wordplay.
'half' suggests halving the letters.
'amid' is an insertion indicator.
'tennis tournament' becomes 'slam' (I am not sure about this - if you are sure you should believe this answer much more).
'lost' with half the letters taken is 'lo'.
'lo' placed inside 'slam' is 'SLALOM'.
Can you help me to learn more?
(Other definitions for slalom that I've seen before include "Type of ski race" , "Downhill skiing race" , "Downhill ski race over a winding course" , "Ski race down zig-zag course" , "Downhill ski event" .)