Familiarise (8)
'familiarise' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for accustom that I've seen before include "get one inured to" , "Maybe reconcile" , "Make (someone) used to (something)" , "Inure" , "Adapt" .)
(Other definitions for acquaint that I've seen before include "Make aware or familiar with, say the facts" , "Get to come to know" , "Familiarise" , "Inform" , "get up to date" .)