Flag hoisted when a ship is about to sail (4,5)
I believe the answer is:
blue peter
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">flag hoisted when a ship is about to sail</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for blue peter that I've seen before include "Flag on ship about to leave port" , "Ship's flag on leaving port" , "Flag flown to warn of a ship's departure" , "Flag flown when about to leave port - TV programme" , "Flag raised before sailing" .)