[Gabriel]

if not Assigned(FClients) then
FClients := TFClients.Create(Application);

// Aqui ja nos aseguramos que esta creado, si no la hemos creado antes
FClients.Show;



// En Formulario Clientes

procedure TFClients.FormClose(Sender: TObject; var Action: TCloseAction);
begin
FClients.Free;
FClients := nil;
end;