Popular musicians become vague (4)
I believe the answer is:
blur
'become vague' is the definition.
(synonyms)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for blur that I've seen before include "Hazy or indistinct image" , "Indistinct appearance like smear" , "Become unclear" , "Make or become indistinct" , "fade" .)