'The police have reassured...'

Please have a look at this:

=> I find the sentence a bit strange because the word ‘anonymity’ seems so dangle (it doesn’t modify any word). Is the sentence right or wrong?

Many thanks,

The witnesses have been guaranteed that they will remain anonymous.

It’s just fine the way it is. Anonymity is a noun, though - it doesn’t modify, but rather you have it. These witnesses will have their anonymity.