Let former pupils time violent disturbance (11)

I believe the answer is:

obstruction

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'let' is the definition.
(thesaurus)

'former pupils time violent disturbance' is the wordplay.
'former pupils' becomes 'OBs' (Old Boy can mean a graduate of a private school).
'time' becomes 't' (abbreviation).
'violent disturbance' becomes 'ruction' (ruction is a kind of disturbance. I am not sure about the 'violent' bit.).
'obs'+'t'+'ruction'='OBSTRUCTION'

Can you help me to learn more?

(Other definitions for obstruction that I've seen before include "Barrier" , "Hindrance to progress" , "Blockage" , "bar" .)

I've seen this clue in The Times.

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