What’s taken into staff about to give treatment (5)
I believe the answer is:
rehab
'treatment' is the definition.
(I have seen 'remedial treatment' mean 'rehab' so perhaps 'treatment' could also mean 'rehab')
'what's taken into staff about' is the wordplay.
'what' becomes 'eh' (I've seen this in other clues).
'taken into' means one lot of letters goes inside another.
'staff' becomes 'bar' (both can mean a pole or stick).
'about' says the letters should be written in reverse.
'bar' backwards is 'rab'.
'eh' placed into 'rab' is 'REHAB'.
'to give' acts as a link.
(Other definitions for rehab that I've seen before include "Treatment for dependency" , "help with addiction" , "Alcohol clinic" , "convalescent home?" , "Place to go, in short, to be restored to fitness" .)