Mean to keep winning, becoming champion (5,2,3)
I believe the answer is:
stand up for
'champion' is the definition.
(I've seen this before)
'mean to keep winning' is the wordplay.
'mean' becomes 'standfor' (standing for is a kind of meaning).
'to keep' is an insertion indicator.
'winning' becomes 'up' (eg being up at half time in football).
'standfor' going around 'up' is 'STAND UP FOR'.
'becoming' acts as a link.
(Other definitions for stand up for that I've seen before include "champion" , "Support" .)