English Translation
He stared at the clear sky for a long time.
The Wiktionary page for cielo raso says that cielo raso means “ceiling” in English (and that page itself references the web page of the RAE).
If I put cielo raso into Google Translate it translates into English as “ceiling”.
The Tatoeba page for this sentence shows that it is a translation from the English sentence “He gazed at the ceiling for a long time.” - again using the word “ceiling” in English for the equivalent of cielo raso in Spanish.
So where has this translation come from using “clear sky” as the English translation of cielo raso? It doesn’t appear to be from an original pairing on Tatoeba - there’s no record of this English translation on the Tatoeba page for this Spanish sentence, either now or in any suggestion of a deleted translation (or on any of the other 4 language pairings that might give a translation-of-a-translation pairing).
The most likely remaining reason that occurs to me is therefore that this is a change that was made due to a user request in Clozemaster using the little red flag.
If this has indeed been a change due to a user report, then I believe that it would be really helpful to have some way of seeing a list of any such changes that have been made over time (or alternatively have some way of putting suggested changes out to the community before those changes are made).