Major tournament is a big hit (9)
I believe the answer is:
grandslam
'major tournament' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'big hit' is the wordplay.
'big' becomes 'grands' (I can't explain this - if you can you should believe this answer much more).
'hit' becomes 'lam' (to 'lam' means to hit hard).
'grands'+'lam'='GRANDSLAM'
'is a' is the link.
Can you help me to learn more?
(Another definition for grandslam that I've seen is " major event".)