Some surreal art simply reflected atmospheric phenomenon (7)
I believe the answer is:
mistral
'atmospheric phenomenon' is the definition.
(mistral is a kind of atmospheric phenomenon)
'some surreal art simply reflected' is the wordplay.
'some' indicates the answer is hidden within the clue (some parts of the word are used).
'reflected' is a reversal indicator (letters reflected back).
'lartsim' can be found hidden inside 'surreal art simply'.
'lartsim' reversed gives 'MISTRAL'.
(Other definitions for mistral that I've seen before include "Cold dry wind in southern France" , "Nice chiller" , "Strong cold dry wind" , "Strong north wind of southern France" , "Famous wind in the Rhone Valley blowing towards the Med" .)