Not knowing the thread had fallen into the ink (2,3,4)
I believe the answer is:
in the dark
'not knowing' is the definition.
(I've seen this before)
'thread had fallen into the ink' is the wordplay.
I cannot really understand how this works, but
an anagram of 'thread' is 'thedar' which is within the answer.
'into' could be 'in' and 'in' is located in the answer.
A single letter 'k' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
'the' is the link.
Can you help me to learn more?
(Other definitions for in the dark that I've seen before include "without being told" , "Not knowing" , "Haviing no information - or light" , "Told nothing" , "after sundown" .)