100 in number for printmaker (6)
I believe the answer is:
etcher
'printmaker' is the definition.
'100 in number' is the wordplay.
'100' becomes 'c' (roman numeral).
'in' is an insertion indicator.
'number' becomes 'ether' (I've seen this before).
'c' put within 'ether' is 'ETCHER'.
'for' acts as a link.
(Other definitions for etcher that I've seen before include "Artist such as Rembrandt" , "One making an impression" , "one may impress deeply" , "Maybe she makes engravings" , "Artist who likes to make an impression?" .)