. . . is one description of this grid (6)
I believe the answer is:
square
'is one description of this grid' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe there's an association between them I don't understand?
This is all the clue.
Can you help me to learn more?
(Other definitions for square that I've seen before include "at right angles to > wicket" , "Type of quadrilateral" , "Centre of cricket ground" , "Old fogey" , "Regular figure" .)