I wrote a riddle for a word about a year ago. I don't know how hard it is, but it becomes pretty obvious after you know the answer. Here it is:

River, Sing, Emit
Rear, Ranging, Mite
An acronym of its measurement
Is the first of synonym
It has no synonym
It has no antonym
Its anagram appears twice
Its clues are a homonym
When it's over, it is up
It controls us - a reality
We control it - a fantasy, imagination
Three of its letters appear in every line
Its third letter is missed in three
What is the word that has been mentioned?

There is no spelling, grammatical or formatting mistake, any such 'mistake' could be intended.

I wrote a riddle for a word about a year ago. I don't know how hard it is, but it becomes pretty obvious after you know the answer. Here it is:

River, Sing, Emit
Rear, Ranging, Mite
An acronym of its measurement
Is the first of synonym
It does not have a synonym
It does not have an antonym
Its anagram appears twice
Its clues are a homonym
When it's over, it is up
It controls us - a reality
We control it - a fantasy, imagination
Three of its letters appear in every line
Its third letter is missed in three
What is the word that has been mentioned?

There is no spelling, grammatical or formatting mistake, any such 'mistake' could be intended.