Having intervals between start and end of summing-up, brilliantly executed (6)

I believe the answer is:

spaced

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'executed' is the definition.
Although both the answer and definition are past participle verbs, I don't understand how one could define the other.

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for spaced that I've seen before include "set some distance apart" , "positioned at intervals" , "Placed at intervals" , "Separated by gaps" , "strung out" .)

I've seen this clue in The Independent.

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