It's a fair amount of time for those expecting break from school (8)
I believe the answer is:
'those expecting break from school' is the definition.
I can't judge whether this definition defines the answer.
'it's a fair amount of time' is the wordplay.
'it's a fair amount of' becomes 'half' (I can't explain this - if you can you should believe this answer much more).
'time' becomes 'term' (I've seen this in other clues).
'half'+'term'='HALFTERM'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for half term that I've seen before include "Short school break" , "Break during division of school year" , "Short school vacation" , "Short holiday during school semester" , "twenty-weeks pregnant?" .)