A long part — Bible without preamble is hard to read (9)
I believe the answer is:
illegible
'hard to read' is the definition.
(I've seen this before)
'a long part bible without preamble' is the wordplay.
I cannot quite see how this works, but
'long' could be 'l' and 'l' is present in the answer.
'part' could be 'leg' (leg is a kind of part) and 'leg' is found in the answer.
This explanation may well be incorrect...
'is' is the link.
Can you help me to learn more?
(Other definitions for illegible that I've seen before include "Too messy to read" , "Unreadable" , "Impossible to read" , "Not capable of being read" , "Not easily read" .)