It's perfect when I give the school a hand (5)
I believe the answer is:
ideal
'it's perfect' is the definition.
(similar in meaning)
'i give the school a hand' is the wordplay.
'give the school' becomes 'dea' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'a hand' becomes 'L' (abbreviation for left, as in the left-hand side).
'i'+'dea'+'l'='IDEAL'
'when' is the link.
Can you help me to learn more?
(Other definitions for ideal that I've seen before include "Nonpareil" , "Utopian; yardstick" , "Textbook" , "fanciful" , "Consummate" .)