It may help Congress by Biden's lead lapsing in X (6)
I believe the answer is:
viagra
'biden's lead lapsing in x' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'it may help congress by' is the wordplay.
I cannot really understand how this works, but
'by' could be 'via' (travelling by or via a place) and 'via' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for viagra that I've seen before include "Drug treating impotence" , "Drug aiding one's sex life" , "Controversial pills" , "Male sexual aid" , "Drug to improve potency" .)