An even chance that contrary drunkard will have an evening meal (6)
I believe the answer is:
tossup
'an even chance' is the definition.
(I've seen this before)
'contrary drunkard will have an evening meal' is the wordplay.
'contrary drunkard will' becomes 'tos' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'have an evening meal' becomes 'sup' (I've seen this in another clue).
'tos'+'sup'='TOSSUP'
'that' is the link.
Can you help me to learn more?
(Other definitions for tossup that I've seen before include "An even chance as determined by coin flip" , "An even chance, like flip of coin" , "A gamble - flip a coin" , "Even chance or risk" , "Flip in the air - it's a gamble" .)