Keeps on about an explosive piece of shrapnel! (5)

I believe the answer is:

harps

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

'keeps on about an explosive piece of shrapnel' is the definition.
I can't judge whether this definition defines the answer.

'keeps on about an explosive piece of' is the wordplay.
'keeps' becomes 'has' (keep can mean to have or possess).
'on' means one lot of letters goes inside another (as in clothing 'on' a person).
'about' shows that the letters should be reversed in order.
'an explosive piece of' becomes 'pr' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'pr' backwards is 'rp'.
'has' going around 'rp' is 'HARPS'.

Can you help me to learn more?

(Other definitions for harps that I've seen before include "Musical instruments of sharp kind" , "Dwells" .)

I've seen this clue in the Evening Standard.

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