I'm guessing that you want something like
SELECT tab1.a, tab2.b, tab3.c, tab4.d
FROM table1 tab1
JOIN table2 tab2 ON (tab1.fg = tab2.fg)
LEFT OUTER JOIN table4 tab4 ON (tab1.ss = tab4.ss)
LEFT OUTER JOIN table3 tab3 ON (tab4.xya = tab3.xya and tab3.desc = 'XYZ')
LEFT OUTER JOIN table5 tab5 on (tab4.kk = tab5.kk AND
tab3.dd = tab5.dd)