Holds up pairs (6)
I believe the answer is:
braces
I believe this clue is a double definition.
'holds up' is the first definition.
(bracing is a kind of holding up)
'pairs' is the second definition.
('brace' can be a synonym of 'pair')
(Other definitions for braces that I've seen before include "Straps used to keep trousers up" , "Dental appliances and pairs" , "Over-the-shoulders supporters" , "Trouser support" , "Stabilises" .)