Telling rash lies about extended study periods? (3-8)

I believe the answer is:

all-nighters

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'extended study periods?' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.

'telling rash lies' is the wordplay.
'telling rash' can be anagrammed to 'ALL-NIGHTERS'.
However, I am not sure how this is indicated.

'about' acts as a link.

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I've seen this clue in The Independent.

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