Fit in (6)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fit in</span>' is the definition.<br/ ><span class="explanation-format__explanation">(to belong somewhere is to fit in there)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for belong that I've seen before include "Be the property of" , "Have a proper place (in)" , "Be correctly assigned" , "Appertain" , "find a place?" .)
(Other definitions for assimilate that I've seen before include "thoroughly understood" , "Absorb and digest (food)" , "Take in and understand" , "Become part of the prevailing culture" , "pick up" .)
(Other definitions for slot that I've seen before include "Scheduled time - hierarchical position" , "Scheduled time -- aperture for coins" , "Hole for e.g. coin" , "Small opening, for a coin say" , "Space for coin or programme" .)