In the Cup, such ties are really punishing! (5)
I believe the answer is:
penal
'punishing' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for penal that I've seen before include "Punitive" , "Involving punishment as by the law" , "Deliberately unpleasant" , "Punishable by law" , "Involving legal punishment" .)