It's a poetic phrase with a couple of interesting aspects:
* "Stella" (star) could refer to a celestial guide, potentially a beacon for sailors.
* "Clavis" (key) suggests unlocking something, perhaps a hidden passage or secret knowledge.
* "Maris" (of the sea) situates this within a maritime context.
* "Indicit" (commands) implies authority and power.
The phrase is often interpreted as a metaphor for the sea, its mysteries, and perhaps even the power of knowledge or navigation. It's not uncommon to find variations of this phrase used in maritime contexts or even in heraldry.