Speyside business making side of that river dry up (6)
I believe the answer is:
scorch
'dry up' is the definition.
(thesaurus)
'speyside business making side of that river' is the wordplay.
I cannot really understand how this works, but
'business' could be 'co' (short for company) and 'co' is found within the answer.
'side' could be 'r' (abbreviation for right) and 'r' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for scorch that I've seen before include "go very fast" , "dry up" , "Wither from exposure to heat" , "career" , "Damage with heat" .)