Schoolboy gutted, almost never in assembly? (7)

'schoolboy gutted almost never in assembly?' is the definition.
I can't tell whether this defines the answer.

'schoolboy gutted almost never in assembly?' is the wordplay.
'gutted' says to hollow out the word (remove centre letters) (to gut something is to remove its insides).
'almost' means to remove the last letter (most of the word but not all of it).
'never' becomes 'no' (I've seen this in other clues).
'in assembly?' becomes 'odic' (I can't justify this - if you can you should give a lot more credence to this answer).
'schoolboy' with its middle removed is 'sy'.
'no' with its final letter removed is 'n'.
'sy'+'n'+'odic'='SYNODIC'

Can you help me to learn more?