Idle fancy about that man, English artist (7)
I believe the answer is:
chimera
'idle fancy' is the definition.
(chimera can mean a fancy or delusion)
'about that man english artist' is the wordplay.
'about' becomes 'c' (abbreviation for 'circa').
'that man' becomes 'him' (I've seen this before).
'english artist' becomes 'era' (I am not sure about this - if you are sure you should believe this answer much more).
'c'+'him'+'era'='CHIMERA'
Can you help me to learn more?
(Other definitions for chimera that I've seen before include "figment of the imagination" , "Mythical creature; delusion" , "phantom" , "wild dream" , "Illusory goal; monster" .)