The term 'buckle down' is an idiom that means to focus and work hard. The crossword solutions for this term are 'APPLY', 'DEVOTE', 'ADDRESS', and 'GIVE'. To 'APPLY' means to put effort into something, while to 'DEVOTE' means to dedicate oneself to a task. To 'ADDRESS' means to take action on a problem, and to 'GIVE' means to put forth effort. Finally, to 'EXERT' means to use energy and strength to do something. All of these words together suggest that the phrase 'buckle down' means to put in a lot of effort and energy to achieve a goal.