Faint copy almost sent out (7)
I believe the answer is:
syncope
'faint' is the definition.
(I know that faint can be written as syncope)
'copy almost sent out' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'sent' with its last letter taken off is 'sen'.
'copy'+'sen'='copysen'
'copysen' is an anagram of 'SYNCOPE'.
(Other definitions for syncope that I've seen before include "Temporary consciousness loss; spy once (anag.)" , "Omission of sounds or letters in middle of word" .)