Current head of school quits physics, say, about little cash at the beginning (10)

'beginning' is the definition.
(I know that incipience is a type of beginning)

'current head of school quits physics say about little cash at' is the wordplay.
I cannot quite see how this works, but
'current' could be 'in' (I've seen this in other clues) and 'in' is found within the answer.
'about' could be 'c' (abbreviation for 'circa') and 'c' is found in the answer.
'cash' could be 'p' (abbreviation for pence) and 'p' is found in the answer.
This explanation may well be incorrect...

'the' acts as a link.

Can you help me to learn more?