Funny boy, certain to succeed (4-2)
I believe the answer is:
odds-on
'certain to succeed' is the definition.
I can't tell whether this definition defines the answer.
'funny boy' is the wordplay.
'funny' becomes 'odd' (I've seen this in another clue).
'boy' becomes 'son' (male child).
'odd'+'son'='ODDS-ON'
Can you help me to learn more?
(Other definitions for odds-on that I've seen before include "More likely to win than lose" , "With success more likely than failure - check with bookie" , "With success more likely as bookie would calculate" , "A better than even chance of success" , "Very likely to happen" .)