Babe's smashed everything in this sport (8)
I believe the answer is:
baseball
'this sport' is the definition.
(baseball is a kind of sport)
'babe's smashed everything' is the wordplay.
'smashed' is an anagram indicator.
'everything' becomes 'all' (all things).
'babes' is an anagram of 'baseb'.
'baseb'+'all'='BASEBALL'
'in' is the link.
(Other definitions for baseball that I've seen before include "Sport played with a bat" , "American game like rounders" , "Lea blabs about the sport" , "Game played badly in the sable lab" , "Game played on a diamond" .)