Artist, retiring, has left in a reckless way (6)
I believe the answer is:
rashly
'in a reckless way' is the definition.
I can't judge whether this definition defines the answer.
'artist retiring has left' is the wordplay.
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'retiring' becomes 'shy' (both can mean reserved or introverted).
'has' means one lot of letters goes inside another.
'left' becomes 'l' (common abbreviation).
'shy' enclosing 'l' is 'shly'.
'ra'+'shly'='RASHLY'
Can you help me to learn more?
(Other definitions for rashly that I've seen before include "In intemperate and injudicious manner" , "Without caution" , "Recklessly" , "Without forethought" , "in reckless fashion" .)