Fundamentals (6)

I think it could be either:

Which length description are you looking for?:

abcs

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

This is all the clue.

(Other definitions for abcs that I've seen before include "Know these to be well versed - alphabetically?" , "12 [THINGS EASY]" , "guides ..." , "Know these letters to be well informed" .)

I've seen this clue in the LA Times, the Universal and The New York Times.

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