Possible Clues:

• Like berries and oysters
• Appropriate to the time of year
• Also sane (anag.)
• Changing through the year
• Beast carries a child according to the time of year
• Occurring at a particular time of the year
• Relating to the time of year
• Unfinished shanty by a lake, suitable for summer, perhaps
• At some times of the year
• Fluctuating through the year