Bishop and wife covering Greek festival, the latest fad (9)
I believe the answer is:
bandwagon
'latest fad' is the definition.
The definition and answer can be both related to thinking as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'bishop and wife covering greek festival' is the wordplay.
'bishop' becomes 'B' (abbreviation for bishop in chess).
'wife' becomes 'w' (abbreviation).
'covering greek festival' becomes 'agon' (I am not sure about this - if you are sure you should believe this answer much more).
'b'+'and'+'w'+'agon'='BANDWAGON'
'the' is the link.
Can you help me to learn more?
(Other definitions for bandwagon that I've seen before include "Vehicle (jumped on when suddenly popular?)" , "Fashionable movement" , "vehicle for musicians" , "Popular movement" , "Suddenly fashionable cause or activity" .)