Breathe irregularly at what should be regular (9)

I believe the answer is:

heartbeat

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

'should be regular' is the definition.
I can't judge whether this definition defines the answer.

'breathe irregularly at' is the wordplay.
'irregularly' is an anagram indicator.
'breathe' is an anagram of 'heartbe'.
'heartbe'+'at'='HEARTBEAT'

'what' acts as a link.

Can you help me to learn more?

(Other definitions for heartbeat that I've seen before include "Essential pulsation" , "Circulation noise" , "Pulse of cardiac origin" , "Animating force" .)

I've seen this clue in The Guardian and The Globe and Mail.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.