Collapse Whitespace() is basically meant for this (you can also use other methods)
Names Default To Here(1);
mystr = "a b";
res1 = Regex(mystr, " +", " ", GLOBALREPLACE);
res2 = Concat Items(Words(mystr, " "), " ");
res3 = Collapse Whitespace(mystr);
show(res1, res2, res3);
Recode has Collapse Whitespace so you can just use that

and it will provide you with a script
// Recode column: Column 6
Local({dt},
dt = Data Table("Big Class");
dt << Begin Data Update;
For Each Row(dt, dt:Column 6[] = Collapse Whitespace(dt:Column 6));
dt << End Data Update;
);
-Jarmo