It takes place at the flat junction (5)
I believe the answer is:
event
'it takes place' is the definition.
(I've seen this before)
'at the flat junction' is the wordplay.
'at' means one lot of letters go next to another.
'the flat' becomes 'even' (level).
'junction' becomes 't'.
'even' put next to 't' is 'EVENT'.
(Other definitions for event that I've seen before include "A thing taking place" , "Something that takes place" , "A notable occurrence or happening" , "Something that happens - part of a programme?" , "Item in sports programme" .)