Apex teaser can really annoy! (10)

I believe the answer is:

exasperate

I'm a little stuck... Click here to teach me more about this clue!

'really annoy' is the definition.
'exasperate' can be an answer for 'annoy' (I've seen this before). I am unsure of the 'really' bit.

'apex teaser can' is the wordplay.
'can' indicates an anagram (I've seen 'canned' mean this (canned can mean drunk)).
'apex'+'teaser'='apexteaser'
'apexteaser' with letters rearranged gives 'EXASPERATE'.

Can you help me to learn more?

(Other definitions for exasperate that I've seen before include "Infuriate" , "Annoy" , "See axe part (anag.)" , "Intensely irritate" , "bug" .)

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

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