Thank you TV and NS for your replies. Yes, I had thought of SEA CHANGE and, it turns out, we are all right! I didn't think of counting the squares and yes, there are six. Sound like a bit more previewing and editing is required in the DT Puzzles office!
Edited to add apologies to the Puzzles staff and to you too of course, , it did say (3,6) so the mistake was mine. *sigh*!