"Age of Aquarius" musical (4)
I believe the answer is:
hair
'age of aquarius musical' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for hair that I've seen before include "Musical with nude scenes" , "Famous hirsute musical with song ` `Aquarius' ' (4)" , "Thread-like structure(s)" , "Threadlike growth" , "Penitent's shirt material" .)