Second date in which fashion is not the main attraction (8)
I believe the answer is:
sideshow
'second date in which fashion is not the main attraction' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Maybe there's an association between them I don't understand?
'second date in which' is the wordplay.
'second' becomes 's' (common abbreviation).
'date' becomes 'ides' (I've seen this before).
'in which' becomes 'how' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
's'+'ides'+'how'='SIDESHOW'
Can you help me to learn more?
(Other definitions for sideshow that I've seen before include "Minor but diverting incident" , "Exhibition subordinate to a larger one" , "Not the main scene of activity" , "Subordinate production to the main event" , "Activity subordinate to a larger one" .)