Gradual assimilation (7)
I believe the answer is:
osmosis
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">gradual assimilation</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 osmosis that I've seen before include "Diffusion; assimilation" , "Absorption (biol.)" , "Large shopping area" , "Process of learning something gradually and without effort" , "absorbing process" .)