Very nearly (6)
'very nearly' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for almost that I've seen before include "Well-nigh" , "As good as" , "Virtually" , "practically" , "Not totally" .)
(Other definitions for just about that I've seen before include "Barely" , "Almost exactly, informally" , "More or less - at the point of starting" , "Almost exactly or completely" .)