Nipple (4)
I believe the answer is:
teat
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">nipple</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that nipple can be written as teat)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for teat that I've seen before include "essential for babies" , "Nipple or dug" , "Bulb on infant's bottle" , "Part of feeding bottle" , "Piece on baby's bottle" .)