On school vacation I attend horror flick - Like A Snake? (10)

'horror flick like a snake?' is the definition.
I can't tell whether this definition defines the answer.

'on school vacation i attend' is the wordplay.
'on' is a charade indicator (letters next to each other).
'vacation' says to hollow out the word (remove centre letters) (middle letters vacate the word).
'attend' becomes 'thering' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'school' with its centre removed is 'sl'.
'sl'+'i' is 'sli'.
'sli'+'thering'='SLITHERING'

Can you help me to learn more?