Sound made by a pigeon (3)
I believe the answer is:
coo
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sound made by a pigeon</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for coo that I've seen before include "Dove-like noise" , "Murmur, speak softly" , "well I never!" , "Avian sound" , "Murmur amorously" .)