A second firm linked to motor-racing debacle (6)
I believe the answer is:
fiasco
'debacle' is the definition.
(I know that debacle can be written as fiasco)
'a second firm linked to motor-racing' is the wordplay.
'second' becomes 's' (common abbreviation).
'firm' becomes 'co' (a firm is a company).
'linked to' means one lot of letters go next to another.
'motor racing' becomes 'fi' (FI resembles F1, Formula 1).
'a'+'s'+'co'='asco'
'asco' put after 'fi' is 'FIASCO'.
(Other definitions for fiasco that I've seen before include "Sudden total disaster" , "Utter failure, debacle" , "A debacle, complete mess" , "An utter mess or cock-up" , "Total cock-up" .)