A cross word

At work there's a small bunch of us who gather at coffee time in the morning (and indeed tea time in the afternoon - though I less often join them for that) to do crosswords. As it's quite a large group we tend to print out six copies of each, and one person fills in the answers while we all join in working them out. Mostly we do the Guardian Cryptic, resorting to the Times Club Monthly and Guardian Genius only in desperation. And we've been working our way through the back catalogue too, since they're available online.

This morning's crossword is by Quantum, Guardian number 22,284 and is about 10 years old. So when we got down to the last clue and we're just a bit stumped as to *why* exactly the answer is correct we can't turn to fifteensquared.com for the solution for a change. The clue is:

Say I'll be in the road or at sea (6)

( Discussion of the answer )

Anyone want to put us out of our misery?