Flash car carrying hip, grand rock group (7,6)
I believe the answer is:
rolling stones
'group' is the definition.
(English rock band)
'flash car carrying hip grand rock' is the wordplay.
'flash car' becomes 'rolls' (Rolls-Royce).
'carrying' indicates putting letters inside.
'hip' becomes 'in' (both can mean fashionable).
'grand' becomes 'G' (G is short for ground as in a thousand).
'rock' becomes 'stone' (synonyms).
'in'+'g'+'stone'='ingstone'
'rolls' going around 'ingstone' is 'ROLLING STONES'.
(Other definitions for rolling stones that I've seen before include "Revolving pebbles" , "Old rockers" , "Group (without moss?)" .)