Age taken by fat old painter? (8)
I believe the answer is:
leonardo
'painter?' is the definition.
(Leonardo is an example)
'age taken by fat old' is the wordplay.
'age' becomes 'eon' (I've seen this before).
'taken by' means one lot of letters goes inside another.
'fat' becomes 'lard' (I've seen this before).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'eon' placed inside 'lard' is 'leonard'.
'leonard'+'o'='LEONARDO'
(Other definitions for leonardo that I've seen before include "First name of da Vinci, great artist" , "Great Italian artist ........ da Vinci" , "Great painter of the Mona Lisa, . . . . . . . . da Vinci" , "So-called code" , "and 12 Across: Renaissance genius" .)