Those from the granite city presumably producing alternative to schist (8)
I believe the answer is:
scottish
'those from the granite city presumably' is the definition.
I can't judge whether this definition defines the answer.
'alternative to schist' is the wordplay.
'alternative' indicates anagramming the letters.
'to'+'schist'='toschist'
'toschist' anagrammed gives 'SCOTTISH'.
'producing' acts as a link.
Can you help me to learn more?
(Other definitions for scottish that I've seen before include "from 18 [MORAY], say?" , "So stitch up to be like Angus or Jock" , "Costs hit this nationality badly" , "tongue" , "From the northern UK" .)