Answer: GOSOUTH

AnswerCrossword Clue
GOSOUTHDeteriorate, slangily
GOSOUTHTurn bad, slangily
GOSOUTHTake a turn for the worse
GOSOUTHMigrate, maybe
GOSOUTHTurn bad
GOSOUTHLeave for the winter, say
GOSOUTHStart to tank
GOSOUTHMigrate for the winter, perhaps
GOSOUTHDecline