Understand there’s to be no declaration (4)
I believe the answer is:
know
'understand' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for know that I've seen before include "Have awareness of" , "Articulated" , "Be sure of something" , "Ken" , "Recognise" .)