About eleven, processed a tube making ore (7)
I believe the answer is:
bauxite
'ore' is the definition.
(thesaurus)
'about eleven processed a tube' is the wordplay.
'about' is an insertion indicator.
'eleven' becomes 'xi' (roman numeral).
'processed' is an anagram indicator.
'a'+'tube'='atube'
'atube' anagrammed gives 'baute'.
'xi' put into 'baute' is 'BAUXITE'.
'making' is the link.
(Other definitions for bauxite that I've seen before include "Ore which contains aluminium" , "Chief ore of aluminium" , "Ore yielding aluminium" , "Mineral" , "Clay-like compound" .)