Crossword Genius

Swear to avoid losing time (4)

Ross

I believe the answer is:

aver

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'swear to' is the definition.
(I've seen this in another clue)

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for aver that I've seen before include "Vera could declare to be true" , "State firmly - even rave about" , "Formally assert" , "'Affirm, assert (4)'" , "State firmly, perhaps rave" .)

I've seen this clue in The Independent.
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