It has a gross square (6)
I believe the answer is:
twelve
This might be a double definition.
'it' is the first definition.
The definition suggests a singular noun which matches the answer.
'a gross square' is the second definition.
The definition and answer can be both quantities as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'has' is the link.
Can you help me to learn more?
(Other definitions for twelve that I've seen before include "Half the number here" , "disciples" , "Three fours" , "Midnight or noon" , "Last hour" .)