Without a bit of towel, bather's back drying out (5)
I believe the answer is:
rehab
I'm afraid I can't even guess how this answer relates to the clue.
Can you help me to learn more?
(Other definitions for rehab that I've seen before include "Treatment for, eg, addiction" , "remedial treatment" , "Place to go, in short, to be restored to fitness" , "Alcohol clinic" , "Restorative care" .)