Remove hems of dressing gown with beating heart (6)

I believe the answer is:

athrob

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

'beating heart' is the definition.
'athrob' can be an answer for 'beating' (I've seen this before). I am not certain of the 'heart' bit.

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for athrob that I've seen before include "Pulsing" , "Pulsating" , "all of a twitter" , "beating" .)

I've seen this clue in The Irish Times.

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