When it gets jammed in an entrance, worry (7)

I believe the answer is:

agitate

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'worry' is the definition.
(thesaurus)

I cannot understand how the rest of the clue works.

(Other definitions for agitate that I've seen before include "Perturb" , "rock" , "Stir; worry" , "Stir; arouse" , "Fluster" .)

I've seen this clue in the Evening Standard.

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