Make sure to lean on inventory (9)
I believe the answer is:
checklist
'inventory' is the definition.
(thesaurus)
'make sure to lean on' is the wordplay.
'make sure' becomes 'check' (synonyms).
'to lean' becomes 'list' (both can mean to tilt).
'on' says to put letters next to each other.
'check'+'list'='CHECKLIST'
(Other definitions for checklist that I've seen before include "sort of schedule" , "Reminder, itemised" , "What's used to verify" , "Items to be performed" .)