Paver's standard weight
I believe the answer is:
flagstone
'paver's' is the definition.
Both the definition and answer are singular nouns.
Perhaps they are linked in a way I don't understand?
'standard weight' is the wordplay.
'standard' becomes 'flag' (I've seen this before).
'weight' becomes 'stone' (stone is a kind of weight).
'flag'+'stone'='FLAGSTONE'
Can you help me to learn more?
(Other definitions for flagstone that I've seen before include "Fine-textured rock" , "Paving slab" , "One walked on" , "It'll lay (some say) at ground level" , "Paving-slab" .)