Rigidly old-fashioned (6)
(Other definitions for square that I've seen before include "Level - shape - piazza - stuffy" , "Centre of cricket ground" , "uncool" , "Type of rectangle" , "New York Times, for example" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">rigidly old-fashioned</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for fusty that I've seen before include "Smelling stale or damp" , "Stale-smelling" .)