Formerly holding name Max? (5)
I believe the answer is:
ernst
'max?' is the definition.
(I've seen this before)
'formerly holding name' is the wordplay.
'formerly' becomes 'erst' (archaic term for formerly or long ago).
'holding' means one lot of letters goes inside another.
'name' becomes 'n' (common abbreviation e.g. on forms).
'erst' going around 'n' is 'ERNST'.
(Other definitions for ernst that I've seen before include "Surrealist; stern (anag.)" , "Young partner" , "He painted" , "artist's name" , "German-born painter, Max, co-founder of dadaism, d. 1976" .)