Not fairly matched in fun event (6)
I believe the answer is:
uneven
'not fairly matched' is the definition.
('uneven' can be a synonym of 'not fairly matched')
'in fun event' is the wordplay.
'in' says the answer is hidden in the clue.
'UNEVEN' is hidden within 'fun event'.
(Other definitions for uneven that I've seen before include "Rough, bumpy" , "Not uniform or smooth" , "Irregular or not smooth" , "Ill-matched - irregular" , "Odd - rough" .)