Standard weight for a paving slab (9)
I believe the answer is:
flagstone
'a paving slab' is the definition.
(I've seen this before)
'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'
'for' is the link.
(Other definitions for flagstone that I've seen before include "Paving-slab" , "Pavior made from Teflon gas" , "Paving slab" , "Fine-textured rock" , "One walked on" .)