Castaway's call for help

SOS

This three-letter distress signal was first adopted in 1908 and is recognized internationally in Morse code as three short, three long, and three short tones.

A castaway stranded at sea would urgently signal for help, and the most famous distress call is "SOS"—a Morse code sequence (three dots, three dashes, three dots) recognized worldwide. The clue plays on the idea of being isolated (a "castaway") and needing rescue, where "call for help" directly hints at this iconic emergency signal. It’s a straightforward definition with no hidden wordplay, relying on the well-known association between shipwrecks and SOS.