SIRDAR is a 6 letter word that starts with S.

1. \Sir*dar"\, n.
   In Turkey, Egypt, etc., a commander in chief, esp. the one
   commanding the Anglo-Egyptian army.
   
   

2. \Sir*dar"\, n. [Hind. & Per. sard[=a]r a chief, general;
   sar the head, top + d[=a]r holding, possessing.]
   A native chief in Hindostan; a headman. --Malcom.