Founding it on units it assembled (11)
I believe the answer is:
institution
'founding' is the definition.
(synonyms)
'it on units it assembled' is the wordplay.
'assembled' indicates an anagram.
'it'+'on'+'units'+'it'='itonunitsit'
'itonunitsit' with letters rearranged gives 'INSTITUTION'.
(Other definitions for institution that I've seen before include "Special needs hospital" , "Large organisation; established custom" , "Established practice" , "residential home" , "Established law or custom" .)