Refers to a person who leads the way, either literally (e.g., a tour guide) or figuratively (e.g., a pioneer in a field).
As the guide of the mountaineering party, he chose a safe route.
彼女は業界の先導者として知られている。
She is known as a leader in the industry.
先導者 stresses someone who physically or metaphorically leads the way at the front, whereas リーダー is the general word for whoever heads a group.
Compound of 先導 (sendō, 'guidance, leading') + 者 (sha, 'person'). The exact historical derivation is uncertain, but the kanji components are conventionally associated with the meaning.