a monkey on (someone's) back

American & Australian

a serious problem that will not go away.

The divorce proceedings are a monkey on her back.

• one and the same
• on earth
• one day
• one-day wonder
• on edge
• one for the books
• one for the road
• One good turn deserves another.
• one-hit wonder
• one-horse race
• one-horse town
• one-man band
• One man's meat is another man's poison.
• on end
• one-night stand
• one of a kind
• one of the boys
• one of the lads
• one of those days
• one-shot
• one step ahead
• One step forward, two steps back.
• one swallow doesn't make a summer
• one thing after another
• one thing leads to another