The leader knocked, ensnared (7)

I believe the answer is:

trapped

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'ensnared' is the definition.
('trap' can be a synonym of 'ensnare')

'the leader knocked' is the wordplay.
'the leader' becomes 't' (I can't justify this - if you can you should believe this answer much more).
'knocked' becomes 'rapped' ('rap' can be a synonym of 'knock').
't'+'rapped'='TRAPPED'

Can you help me to learn more?

(Other definitions for trapped that I've seen before include "Ensnared, cornered" , "Stuck" , "in a tight corner" , "Snared" , "Caught" .)

I've seen this clue in The Daily Express.

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