Youngster providing the school head with grub (5)
I believe the answer is:
sprog
'youngster providing' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'school head with grub' is the wordplay.
I cannot quite see how this works, but
'school' could be 's' and 's' is found in the answer.
The remaining letters 'prog' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'the' acts as a link.
Can you help me to learn more?
(Other definitions for sprog that I've seen before include "Infant" , "Child; recruit (mil. slang)" , "Child, colloquially" , "Kid" , "Baby (slang)" .)