Reportedly isn't tied up? (4)
I believe the answer is:
knot
'up?' is the definition.
Although both the answer and definition are verbs in their base form, I cannot understand how one could define the other.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for knot that I've seen before include "Unit of speed used by ships" , "Granny or reef, perhaps?" , "Tangle; sandpiper" , "Shore bird, tangle" , "A sheepshank or bowline" .)