Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
clutter [ˈklʌtər] vt (also: clutter up)(room, table) захламля́ть (захлами́ть*perf)
n хлам
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
Русский: