Car seen racing over 100 by groups of spectators (9)
I believe the answer is:
audiences
'groups of spectators' is the definition.
'car seen racing over 100' is the wordplay.
'car' becomes 'audi' (audi is a german car brand**).
'racing' is an anagram indicator (to race around can mean to move).
'over' indicates putting letters inside.
'a00' becomes 'c' ('C' can be a synonym of 'a00').
'seen' with letters rearranged gives 'enes'.
'enes' enclosing 'c' is 'ences'.
'audi'+'ences'='AUDIENCES'
'by' acts as a link.
(Another definition for audiences that I've seen is " Sad Eunice found among stage watchers".)