Works up references in support of unopened congress (7)
I believe the answer is:
excites
'works up' is the definition.
(work up can mean to excite)
'references in support of unopened congress' is the wordplay.
'references' becomes 'cites' ('cite' can be a synonym of 'reference').
'in support of' says to put letters next to each other (in a down clue, some letters hold others up).
'unopened' means to remove the first letter (without opening letter).
'congress' becomes 'sex' (I've seen this in another clue).
'sex' with its initial letter taken off is 'ex'.
'cites' put after 'ex' is 'EXCITES'.
(Other definitions for excites that I've seen before include "Kindles" , "Makes eager" , "Arouses feelings in" , "Thrills" , "Stirs up, rouses" .)