Half chance rugby doesn't start (5)
I believe the answer is:
evens
'half chance' is the definition.
'evens' can be an answer for 'chance' (I've seen this before). I am not sure about the 'half' bit.
'rugby doesn't start' is the wordplay.
'rugby' becomes 'sevens' (I've seen this before).
'doesn't start' means to remove the first letter.
'sevens' with its first letter taken off is 'EVENS'.
Can you help me to learn more?
(Other definitions for evens that I've seen before include "Smooths the odds" , "square" , "Odds offering equal chance of win or lose" , "Level odds?" , "50-50 odds" .)