Army officer engaging a second person to make plan (6)
I believe the answer is:
layout
'plan' is the definition.
(layout is a kind of plan)
'army officer engaging a second person' is the wordplay.
'army officer' becomes 'lt' (I've seen this in other clues).
'engaging' means one lot of letters goes inside another.
'second person' becomes 'you' (I've seen this before).
'a'+'you'='ayou'
'lt' enclosing 'ayou' is 'LAYOUT'.
'to make' acts as a link.
(Other definitions for layout that I've seen before include "Disposition" , "disposal together?" , "Arrangement of text and pictures on a page" , "Arrangement of a printed page" , "Arrangement of page, buildings, etc" .)