On their game, perhaps, some found tossing a used caber (5,5)
I believe the answer is:
bread sauce
'on their game perhaps some' is the definition.
I can't tell whether this definition defines the answer.
'tossing a used caber' is the wordplay.
'tossing' indicates anagramming the letters.
'a'+'used'+'caber'='ausedcaber'
'ausedcaber' with letters rearranged gives 'BREAD SAUCE'.
'found' is the link.
Can you help me to learn more?
(Other definitions for bread sauce that I've seen before include "Accompaniment for turkey?" , "something creamy and white?" , "Food dressing" , "chicken might come with it" , "[TRIMMING] ? - with 10a" .)