Distorted notes in passport, say, held by a decrepit thing (4,4)
I believe the answer is:
acid rock
'distorted notes' is the definition.
(genre of music using distortion)
'passport say held by a decrepit thing' is the wordplay.
'passport say' becomes 'ID' (a passport is identification).
'held by' indicates putting letters inside.
'decrepit thing' becomes 'crock' (crock can mean something decrepit or broken).
'a'+'crock'='acrock'
'id' put inside 'acrock' is 'ACID ROCK'.
'in' acts as a link.
(Other definitions for acid rock that I've seen before include "Style of popular music" , "Supposedly drug-inspired musical style" .)