Callow youth's assignation with Jan, initially? (5,4)

'callow youth's' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'assignation with jan initially?' is the wordplay.
I cannot quite understand how this works, but
'assignation' could be 'date' (an assigned meeting) and 'date' is located in the answer.
'initially?' could be 'first' (I've seen this in another clue) and 'first' is located in the answer.
No letters remain.
This explanation may well be incorrect...

Can you help me to learn more?