Singer, very good, keeping musical work organised (7)
I believe the answer is:
soprano
'singer' is the definition.
(I've seen this before)
'very good keeping musical work organised' is the wordplay.
'very good' becomes 'so' (as in the adjectival form 'just so!').
'keeping' means one lot of letters goes inside another.
'musical work' becomes 'op' (abbreviation for opus).
'organised' becomes 'ran' (I've seen this before).
'op'+'ran'='opran'
'so' enclosing 'opran' is 'SOPRANO'.
(Other definitions for soprano that I've seen before include "Highly vocal musician" , "Singer who aims high" , "Norman, perhaps" , "Singer of high notes" , "Woman singing" .)