Develop; become larger (4)
I believe the answer is:
grow
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">develop</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that develop can be written as grow)</span><br/ ><br/ >'<span class="explanation-format__original">become larger</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ ></span>
(Other definitions for grow that I've seen before include "Mature" , "Gain in size" , "Develop; increase" , "Multiply" , "Become larger" .)