Does anybody know the origin of the phrase 'clued up'?
etymonline has this hint about "to clue" as a verb
1590s, phonetic variant of clew "a ball of thread or yarn," with reference to the one Theseus used as a guide out of the Labyrinth. The purely figurative sense of "that which points the way" is from 1620s. The verb meaning "to inform someone of the important facts" is attested by 1934.
So the etymological "thread" is a follows
"clew" (Theseus thread provided by Ariadne) => "clue" => "to clue (someone)" => "to be clued".
There is also a different, but related, meaning in the nautical domain: [OED]
to draw the lower ends or clews (of sails) up to the upper yard or the mast in preparation for furling or for making ‘goose-wings’
but in this case, the preferred spelling is "clew up".