Traditional notes of musk oil mixed in case of fabric (4,5)
I believe the answer is:
folk music
'traditional notes' is the definition.
(I've seen this before)
'musk oil mixed in case of fabric' is the wordplay.
'mixed' indicates an anagram.
'in' means one lot of letters goes inside another.
'case of' suggests removing the centre (outsides of).
'fabric' with its middle removed is 'fc'.
'musk'+'oil'='muskoil'
'muskoil' anagrammed gives 'olkmusi'.
'olkmusi' placed within 'fc' is 'FOLK-MUSIC'.
'of' is the link.
(Other definitions for folk music that I've seen before include "Traditional songs and dances" , "traditional notes" .)