Black bird; boast (4)
I believe the answer is:
crow
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">black bird</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">boast</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(to crow about something is to boast about it)</span><br/ ><br/ ></span>
(Other definitions for crow that I've seen before include "Large black bird" , "Brag; carrion bird" , "shout in triumph" , "Bird in 1's poems" , "Express triumph; bird" .)