Wearies Irish king on Sunday (4)

I believe the answer is:

irks

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'wearies' is the definition.
Although both the answer and definition are verbs in their -s form, I cannot understand how one could define the other.

'irish king on sunday' is the wordplay.
'irish' becomes 'Ir' (abbreviation).
'king' becomes 'k' (abbreviation for king in chess).
'on' means one lot of letters go next to another.
'sunday' becomes 's'.
'ir'+'k'+'s'='IRKS'

Can you help me to learn more?

(Other definitions for irks that I've seen before include "Annoys, irritates" , "'Irritate, annoy (4)'" , "Annoys, vexes" , "Galls" .)

I've seen this clue in the Sydney Morning Herald.

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