Car to go wrong on a boring day (7)
I believe the answer is:
ferrari
'car' is the definition.
'go wrong on a boring day' is the wordplay.
'go wrong' becomes 'err' (I've seen this before**).
'on' says to put letters next to each other.
'boring' indicates putting letters inside (some letters must 'bore' a hole into other letters).
'day' becomes 'fri'.
'err'+'a'='erra'
'erra' put into 'fri' is 'FERRARI'.
'to' acts as a link.
(Other definitions for ferrari that I've seen before include "Italian racing car company" , "Sports car brand" , "Italian sports car" , "Type of racing car" .)