Having a better than even chance (4-2)
I believe the answer is:
odds-on
'having a better than even chance' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for odds-on that I've seen before include "Bookie's assessment of success being more likely than failure" , "With success more likely than favour in bookie's phrase" , "Very likely to happen" , "With success more likely than failure - check with bookie" , "More likely to win than lose" .)