Time of day when engine breaks down - about five (7)
I believe the answer is:
evening
'time of day' is the definition.
(I've seen this before)
'engine breaks down about five' is the wordplay.
'breaks down' indicates an anagram.
'about' is an insertion indicator.
'five' becomes 'V' (Roman numeral).
'engine' with letters rearranged gives 'eening'.
'eening' enclosing 'v' is 'EVENING'.
'when' acts as a link.
(Other definitions for evening that I've seen before include "Calming" , "Making uniform" , "Preparing flat" , "Subject of nocturne" , "'Soup of the - - '" .)