Funny boy, more likely to succeed than not? (4-2)
I believe the answer is:
odds-on
'more likely to succeed than not?' is the definition.
(more likely to happen than not)
'funny boy' is the wordplay.
'funny' becomes 'odd' (I've seen this in another clue).
'boy' becomes 'son' (synonyms).
'odd'+'son'='ODDS-ON'
(Other definitions for odds-on that I've seen before include "A better than even chance of success" , "With success more likely than failure - check with bookie" , "Better than evens" , "With favourable chances" , "Bookie's assessment of success being more likely than failure" .)