Where clause in a XML column
drop table t1 purge;
create table t1 (id number, cxml clob);
insert into t1 values (1,
'&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;l-analysis version="2.9"&gt;
   &lt;vehicle&gt;
      &lt;odo-reading latest="true"&gt;
         &lt;reading value="653463"&gt;653,463&lt;/reading&gt;
         &lt;reading-date value="2018-12-04"&gt;4-Dec-2018&lt;/reading-date&gt;
         &lt;reading-unit code="K"&gt;Km&lt;/reading-unit&gt;
      &lt;/odo-reading&gt;
  &lt;odo-reading latest="false"&gt;
     &lt;reading value="391264"&gt;393,264&lt;/reading&gt;
     &lt;reading-date value="2018-12-04"&gt;4-Dec-2018&lt;/reading-date&gt;
     &lt;reading-unit code="K"&gt;Km&lt;/reading-unit&gt;
  &lt;/odo-reading&gt;
   &lt;/vehicle&gt;
&lt;/l-analysis&gt;');
commit;

select extractvalue(xmltype(cxml), 'l-analysis/vehicle/odo-reading[@latest="true"]/reading/@value') as value from t1;

VALUE     
----------
653463


Answer to the original question before it was edited:

drop table t1 purge;
create table t1 (id number, cxml clob);
insert into t1 values (1,
'&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;l-analysis version="2.9"&gt;
   &lt;vehicle&gt;
      &lt;odo-reading latest="true"&gt;
         &lt;reading value="653463"&gt;653,463&lt;/reading&gt;
         &lt;reading-date value="2018-12-04"&gt;4-Dec-2018&lt;/reading-date&gt;
         &lt;reading-unit code="K"&gt;Km&lt;/reading-unit&gt;
      &lt;/odo-reading&gt;
   &lt;/vehicle&gt;
&lt;/l-analysis&gt;');
insert into t1 values (2,
'&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;l-analysis version="2.9"&gt;
   &lt;vehicle&gt;
      &lt;odo-reading latest="false"&gt;
         &lt;reading value="653463"&gt;653,464&lt;/reading&gt;
         &lt;reading-date value="2018-12-04"&gt;4-Dec-2018&lt;/reading-date&gt;
         &lt;reading-unit code="K"&gt;Km&lt;/reading-unit&gt;
      &lt;/odo-reading&gt;
   &lt;/vehicle&gt;
&lt;/l-analysis&gt;');
commit;

select id, extractvalue(xmltype(cxml), 'l-analysis/vehicle/odo-reading/reading/@value') as value from t1
where extractvalue(xmltype(cxml), 'l-analysis/vehicle/odo-reading/@latest') = 'true';   

        ID VALUE     
---------- ----------
         1 653463