Prepares for couples (6)
I believe the answer is:
braces
I believe this clue is a double definition.
'prepares' is the first definition.
(bracing is a kind of preparing)
'couples' is the second definition.
('brace' can be a synonym of 'couple')
'for' acts as a link.
(Other definitions for braces that I've seen before include "Support for trousers" , "Dental appliances and pairs" , "bolsters" , "Couples" , "Stabilises" .)