Artist in autumn shows weather phenomenon (8)
I believe the answer is:
rainfall
'weather phenomenon' is the definition.
'rainfall' can be an answer for 'phenomenon' (rainfall is a kind of phenomenon). I'm unsure of the 'weather' bit.
'artist in autumn' is the wordplay.
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'autumn' becomes 'fall' (synonyms).
'ra'+'in'+'fall'='RAINFALL'
'shows' is the link.
Can you help me to learn more?
(Other definitions for rainfall that I've seen before include "Water falling in drops" , "Amount of water coming down" , "Precipitation, get out umbrella" , "Shower" , "Climate measure" .)