One at the corner of a diamond? (4)
I believe the answer is:
base
This might be a double definition.
'one' is the first definition.
The answer and definition can be both quantities as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'the corner of a diamond?' is the second definition.
(I've seen this in another clue)
'at' is the link.
Can you help me to learn more?
(Other definitions for base that I've seen before include "Bottom support" , "Not a noble" , "Foundation; counterfeit" , "This underlying structure" , "Mil. operations centre" .)