I will shortly get accustomed to being maltreated (3-4)
I believe the answer is:
ill-used
'being maltreated' is the definition.
(I've seen this before)
'i will shortly get accustomed' is the wordplay.
'i will shortly' becomes 'Ill' (abbreviation; 'shortly' indicates a short form).
'get' says to put letters next to each other.
'accustomed' becomes 'used' (I've seen this before).
'ill'+'used'='ILL-USED'
'to' is the link.
(Other definitions for ill-used that I've seen before include "Badly treated, exploited" , "Maltreated" , "Mistreated" .)