Swear as dance party beginning to end? (4)
I believe the answer is:
aver
'swear' is the definition.
(synonyms)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for aver that I've seen before include "State; say" , "State firmly, propound" , "Formally assert" , "Declare or insist" , "State decisively" .)