Good to deliver box (4)
I believe the answer is:
grid
'box' is the definition.
(a grid is a square design)
'good to deliver' is the wordplay.
'good' becomes 'g' (abbreviation).
'to deliver' becomes 'rid' (e.g. deliver us from evil).
'g'+'rid'='GRID'
(Other definitions for grid that I've seen before include "Lattice, mesh" , "Network of horizontal andvertical lines" , "Regular pattern of horizontal and vertical lines" , "This crossword structure" , "Crossword pattern" .)