Grow together, fuse (8)
I believe the answer is:
coalesce
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">grow together</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >'<span class="explanation-format__original">fuse</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that fuse can be written as coalesce)</span><br/ ><br/ ></span>
(Other definitions for coalesce that I've seen before include "Combine and form one whole, as political parties may" , "Combine with others as political parties may do" , "Grow together, amalgamate" , "To bring together" , "blend" .)