Another name for Jason? (5)

'jason?' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'another name' is the wordplay.
I cannot really understand how this works, but
'name' could be 'jon' and 'jon' is found within the answer.
The remaining letters 'as' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...

'for' acts as a link.

Can you help me to learn more?