Inspiring figure's French art includes later 'Man with Sieve' (12)
I believe the answer is:
eratosthenes
'man with sieve' is the definition.
I can't tell whether this defines the answer.
'inspiring figure's french art includes later' is the wordplay.
'inspiring figure's' becomes 'erato's' (muse of poetry in Greek mythology).
'french art' becomes 'es' ('is' in French - 'art' can mean 'is' eg 'thou art').
'includes' means one lot of letters goes inside another.
'later' becomes 'then' (I've seen this in another clue).
'eratos'+'es'='eratoses'
'eratoses' going around 'then' is 'ERATOSTHENES'.
Can you help me to learn more?
(Other definitions for eratosthenes that I've seen before include "mathematician" , "old astronomer" .)