Strain of working in stone (7)
I believe the answer is:
tension
'strain' is the definition.
(I know that tension is a type of strain)
'working in stone' is the wordplay.
'working' indicates an anagram.
'in'+'stone'='instone'
'instone' with letters rearranged gives 'TENSION'.
'of' is the link.
(Other definitions for tension that I've seen before include "Assay" , "Strained state" , "anxious state" , "nerves" , "One isn't (anag.)" .)