Trendy, on end of street, a Parisian flat? No! (2,4)
I believe the answer is:
in tune
'flat? no' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'trendy on end of street a parisian' is the wordplay.
'trendy' becomes 'in'.
'on' says to put letters next to each other.
'end of' says to take the final letters.
'a parisian' becomes 'une' ('a' in French).
The final letter of 'street' is 't'.
'in'+'t'+'une'='IN TUNE'
Can you help me to learn more?
(Other definitions for in tune that I've seen before include "Conversant" , "agreeing" , "Playing or singing at the correct musical pitch" .)