Star's bedtime (6)
I believe the answer is:
sunset
'star's bedtime' is the definition.
The definition and answer can be both related to time as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'star's bedtime' is the wordplay.
'star's' becomes 'suns' (Sun is an example).
'bedtime' becomes 'et' (I can't explain this - if you can you should give a lot more credence to this answer).
'suns'+'et'='SUNSET'
Can you help me to learn more?
(Other definitions for sunset that I've seen before include "Describes a declining industry or technology" , "Dusk" , "US nest (anag.)" , "Musical from film about Hollywood" , "When the light begins to fall below the horizon" .)