Hazard youngster comes across (7,2)

'comes across' is the definition.
(to chance on something is to come across it)

'hazard youngster' is the wordplay.
I cannot quite understand how this works, but
'hazard' could be 'chance' (hazard can mean chance) and 'chance' is found within the answer.
'youngster' could be 'son' (a child) and 'son' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...