Like a social structure expected to return in autumn? Not entirely (6)
I believe the answer is:
feudal
'like a social structure' is the definition.
I can't judge whether this defines the answer.
'expected to return in autumn? not entirely' is the wordplay.
'expected' becomes 'due' (similar in meaning).
'to return' shows that the letters should be reversed in order.
'in' indicates putting letters inside.
'autumn?' becomes 'fall' ('fall' can be a synonym of 'autumn').
'not entirely' means to remove the last letter.
'due' written backwards gives 'eud'.
'fall' with its last letter taken away is 'fal'.
'eud' inserted within 'fal' is 'FEUDAL'.
Can you help me to learn more?
(Other definitions for feudal that I've seen before include "Pertaining to old social system" , "Relating to vassalage" , "Medieval in approach" , "Reactionary" , "Pertaining to fiefs" .)