Election success for party once more? (5)
I believe the answer is:
again
'once more?' is the definition.
('again' can be a synonym of 'once more')
'election success for' is the wordplay.
I cannot quite understand how this works, but
'success' could be 'gain' and 'gain' is present in the answer.
A single letter 'a' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'party' is the link.
Can you help me to learn more?
(Other definitions for again that I've seen before include "second term" , "10 10 [AGAIN" , "'Another time, once more (5)'" , "Predictably perhaps" , "Moreover - a second time" .)