A pair to hold up (5)
I believe the answer is:
brace
This clue is a double definition.
'a pair' is the first definition.
('brace' can be a synonym of 'pair')
'hold up' is the second definition.
(bracing is a kind of holding up)
'to' is the link.
(Other definitions for brace that I've seen before include "Teeth straightener" , "Secure" , "Strengthen; pair" , "hand tool" , "Two of a kind" .)