Accidental (4)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">accidental</span>' is the definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for flat that I've seen before include "Personal residence" , "Pied-a-terre" , "Apartment - on the level" , "Even - somewhere to live" , "without qualification" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">accidental</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for casual that I've seen before include "Informal or blase" , "displaying lack of commitment" , "Insouciant" , "Informal or not showing commitment" , "Informal or happening by chance" .)