Annoy police informer (4)

I believe the answer is:

nark

I believe this is a double definition.

'annoy' is the first definition.
('nark' can be a synonym of 'annoy')

'police informer' is the second definition.
(I've seen this before)

(Other definitions for nark that I've seen before include "Police spy" , "Cause minor annoyance" , "Annoy (colloq.); informer" , "Annoy; police informer" , "Nettle - informer" .)

I've seen this clue in The Telegraph, The Times and The Guardian.

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