Keep going on about Prahran's lost supporters (4)

I believe the answer is:

harp

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'keep' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for harp that I've seen before include "David's instrument" , "Heavenly instrument?" , "Traditional Gaelic musical instrument" , "Instrument (for angels?)" , "semitone higher, abandoning intro" .)

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

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