Acid oddly cold for sun treatment (8)
'acid' is the definition.
Both the answer and definition are adjectives. Maybe they are linked in a way I don't understand?
'oddly cold for sun treatment' is the wordplay.
'oddly' indicates alternate letters (letters in the odd-numbered positions are used).
'treatment' indicates anagramming the letters.
The alternate letters of 'cold' are 'cl'.
'clforsun' with letters rearranged gives 'SCORNFUL'.
Can you help me to learn more?
(Other definitions for scornful that I've seen before include "Disdainful, contemptuous", "Openly contemptuous", "sneering?", "Showing contempt for", "Contemptuous or derisory".)