Star -- British -- in Speed (9)
I believe the answer is:
celebrity
'star' is the definition.
(star can mean a famous person)
'british in speed' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'in' is an insertion indicator.
'speed' becomes 'celerity' (celerity is a kind of speed).
'b' placed inside 'celerity' is 'CELEBRITY'.
(Other definitions for celebrity that I've seen before include "name" , "Star" , "target of paparazzo?" , "Fame" , "Famous person seen in rebel city" .)