Tweet endlessly about large victory number (6)
I believe the answer is:
twelve
'number' is the definition.
(twelve is a kind of number)
'tweet endlessly about large victory' is the wordplay.
'endlessly' means to remove the last letter.
'about' indicates putting letters inside.
'large' becomes 'L' (eg in clothes sizes).
'victory' becomes 'v'.
'tweet' with its last letter taken away is 'twee'.
'l'+'v'='lv'
'twee' going around 'lv' is 'TWELVE'.
(Other definitions for twelve that I've seen before include "AM/PM separator?" , "houses in a year?" , "Apostles and members of the jury" , "Half the number here" , "disciples" .)