also: たんちょ
We found a clue to solving the case.
研究の端緒は小さな疑問から始まった。
The beginning of the research started from a small question.
The police found the first lead toward solving the case.
That discovery became the starting point for new research.
This treaty opened the way toward improved relations between the two countries.
糸口 is a slightly more everyday word for a small clue that lets you start unraveling a problem, while 端緒 sounds more formal and literary.
手がかり is the common word for a clue or lead in everyday speech, while 端緒 is more literary and can also mean the very start of something.
始まり is a general word for 'beginning' usable in any context, while 端緒 is formal and often implies the initial clue or trigger that leads to something.
きっかけ is a casual, everyday word for an opportunity or trigger that starts something, while 端緒 is used in stiff, formal writing.
Standard kanji spelling; the reading たんしょ is the most common.
Alternate reading; less common than たんしょ.
端 (edge, beginning) + 緒 (thread, beginning). The combination suggests the 'thread' that leads to the start of something.