Time for us to return to the nest, possibly (6)
I believe the answer is:
sunset
'time' is the definition.
(I know that sunset is a type of hour)
'us to return to the nest possibly' is the wordplay.
'to return' says the letters should be written backwards.
'to' says to put letters next to each other.
'possibly' indicates an anagram.
'us' written backwards gives 'su'.
'nest' with letters rearranged gives '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" .)