Breakdown company tails Italian cars, ignoring Tesla (6)
I believe the answer is:
fiasco
'breakdown' is the definition.
(fiasco is a kind of breakdown)
'company tails italian cars ignoring tesla' is the wordplay.
'company' becomes 'co' (abbreviation).
'tails' is a charade indicator (letters next to each other) (tail can mean to follow).
'italian cars' becomes 'fiats' (I've seen this in another clue).
'ignoring' is a deletion indicator.
'tesla' becomes 'T' (scientific unit).
'fiats' with 't' removed is 'fias'.
'co' after 'fias' is 'FIASCO'.
(Other definitions for fiasco that I've seen before include "A debacle, complete mess" , "Ridiculous and total failure" , "An absolute mess, what a farce" , "Humiliating disaster" , "washout" .)