Gently fading but fashionable duo in denim (10)
I believe the answer is:
diminuendo
'gently fading' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'fashionable duo in denim' is the wordplay.
'fashionable' indicates anagramming the letters (letters can be fashioned into something else).
'duo'+'in'+'denim'='duoindenim'
'duoindenim' with letters rearranged gives 'DIMINUENDO'.
'but' acts as a link.
Can you help me to learn more?
(Other definitions for diminuendo that I've seen before include "Getting quieter" , "Decrease in loudness" , "Making less sound" , "Letting sound fade away" , "losing force" .)