Maybe opposing women’s teams in cup tie: one’s knocked out (6)
I believe the answer is:
sexism
'maybe opposing women's' is the definition.
I can't judge whether this definition defines the answer.
'teams in cup tie one's knocked out' is the wordplay.
'teams' becomes 'xis' (I can't explain this - if you can you should give a lot more credence to this answer).
'in' indicates putting letters inside.
'cup tie' becomes 'semi' (semi-final is a type of cup tie).
'one' becomes 'i' (Roman numeral).
'knocked out' suggests deleting specific letters.
'semi' with 'i' removed is 'sem'.
'xis' going into 'sem' is 'SEXISM'.
Can you help me to learn more?
(Other definitions for sexism that I've seen before include "Discrimination (against women?)" , "Prejudice based on gender" , "Discrimination on grounds of gender" , "Gender-based discrimination" , "Discrimination on the basis of gender" .)