Drawings -- a hundred by artist, that initiator of surrealism (7)
I believe the answer is:
crayons
'drawings' is the definition.
(can refer to particular drawings done with crayons)
'a hundred by artist that initiator of surrealism' is the wordplay.
'a hundred' becomes 'c' (Roman numeral).
'by' says to put letters next to each other.
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'that' becomes 'yon' (archaic term meaning 'that').
'initiator of' indicates taking the first letters.
The first letter of 'surrealism' is 's'.
'c'+'ra'+'yon'+'s'='CRAYONS'
(Other definitions for crayons that I've seen before include "colours" , "Coloured sticks for drawing" , "Coloured writing sticks" , "Wax pencils" .)