Work at last in stone (6)
I believe the answer is:
cobble
This clue is a double definition.
'work at last' is the first definition.
(I've seen this before)
'stone' is the second definition.
(I know that cobble is a type of paving stone)
'in' is the link.
(Other definitions for cobble that I've seen before include "part of road surface" , "What a shoe repairer does" , "Stone used in road surfaces" , "Patch up; road stone" , "Put together" .)