Time for us to return to the nest, possibly (6)
I believe the answer is:
sunset
'time' is the definition.
(sunset is a kind of time)
'us to return to the nest possibly' is the wordplay.
'to return' says the letters should be written backwards.
'to' is a charade indicator (letters next to each other).
'possibly' is an anagram indicator.
'us' back-to-front is 'su'.
'nest' is an anagram of 'nset'.
'su'+'nset'='SUNSET'
'for' is the link.
(Other definitions for sunset that I've seen before include "The fading light of evening" , "Onset of night" , "This in west" , "Dusk" , "Time of evening colour" .)