Meant to endorse the document enclosed (8)
I believe the answer is:
designed
'meant' is the definition.
(I've seen this before)
'endorse the document enclosed' is the wordplay.
I cannot really understand how this works, but
'endorse' could be 'sign' (I've seen this before) and 'sign' is found in the answer.
'document' could be 'deed' (deed is a kind of document) and 'deed' is located in the leftover letters.
This accounts for all the letters.
This explanation may well be incorrect...
'to' acts as a link.
Can you help me to learn more?
(Other definitions for designed that I've seen before include "Made a drawing or blueprint" , "Conceived of and produced 3dn" , "Conceived and drew something" , "Make a drawing or blueprint" , "Planned or created" .)