Something that happens with flat tyre initially (5)
I believe the answer is:
event
'something that happens' is the definition.
(I've seen this before)
'with flat tyre initially' is the wordplay.
'with' is a charade indicator (letters next to each other).
'flat' becomes 'even' (level).
'initially' indicates taking the first letters.
The initial letter of 'tyre' is 't'.
'even'+'t' is 'EVENT'.
(Other definitions for event that I've seen before include "pole vault maybe" , "celebration?" , "What will happen" , "important" , "match" .)