Signal to proceed (3)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">signal to proceed</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 green light that I've seen before include "Signal of consent" , "Go-ahead" , "OK" , "something to go on" , "What one has to go on" .)
(Other definitions for nod that I've seen before include "Indicate assent or recognition" , "Move head in agreement" , "Tacit agreement" , "Drowse" , "Cain left Eden for the Land of . . ." .)