Sulphur, say, on a lake, is atmospheric (9)
I believe the answer is:
elemental
'atmospheric' is the definition.
Both the answer and definition are adjectives. Maybe you can see a link between them that I can't see?
'sulphur say on a lake' is the wordplay.
'sulphur say' becomes 'element' (sulphur is a kind of element).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'lake' becomes 'L' (geographical abbreviation).
'element'+'a'+'l'='ELEMENTAL'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for elemental that I've seen before include "radical" , "being like Mercury?" , "Basic, primitive" , "Fundamental; supernatural entity" , "Let me lean like forces of nature" .)