Composer having to live invested in unstable groschen (10)
I believe the answer is:
schoenberg
'composer' is the definition.
(I know that Schoenberg is a composer)
'to live invested in unstable groschen' is the wordplay.
'to live' becomes 'be' (synonyms).
'invested in' indicates putting letters inside.
'unstable' indicates an anagram.
'groschen' is an anagram of 'schoenrg'.
'be' placed within 'schoenrg' is 'SCHOENBERG'.
'having' is the link.
(Other definitions for schoenberg that I've seen before include "Arnold --, Austrian-born composer" , "Austrian scorer" .)