Here's the song as it is on the album. Your missing word I first thought might bes brig, but on listening closely it definitely seems to end with /k/ and does indeed seem to be break. (Break cargo was cargo that had to be loaded individually not in bulk; I don't know if that's significant!),There are two other differences, the one in v1 significant.

Mick

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HARBOUR VOICE
(Sean Cooney)

I hear a voice singing in the harbour
Calling me to dream;
But it's only the ghost of a song
Singing in a time that's been.

I see a ship sailing past the pierhead
Calling me to sing;
But it's only the ghost of a break
With nothing left to bring.

I see two forms wrapped up in the moonlight
Calling me to cry;
But they're only the ghost of a love
That promised not to die."

I hear a voice singing in the harbour
Calling me to dream;
But it's only the ghost of a song
Singing in a time that's been.

I hear a voice singing in the harbour


Source: The Young'Uns, album When Our Grandfathers Said No>/b>