This is the 9188th most frequent Russian word.
сино
The word "сино" does not appear to have a standalone meaning in Russian; it may be a misspelling or abbreviation.
Here, 'сино' could theoretically mean 'beyond' or 'near', though it's not commonly used this way in modern Russian.
Солнце встало утром сино облаков.
The sun rose in the morning beyond the clouds.
In this context, 'сино' could imply proximity, albeit rarer usages in historical dialects.
Я вижу сино дверей.
I see near the doors.
Here 'сино' could imply 'near to', though it is archaic.