Rude, popular and very fast (8)
I believe the answer is:
insolent
'rude' is the definition.
(thesaurus)
'popular and very fast' is the wordplay.
'popular' becomes 'in'.
'and' says to put letters next to each other.
'very' becomes 'so' (I've seen this in other clues).
'fast' becomes 'lent' (I've seen this before).
'in'+'so'+'lent'='INSOLENT'
(Other definitions for insolent that I've seen before include "Extremely fresh" , "Rude and disrespectful" , "Rudely disrespectful" , "Bold" , "Rude, showing lack of respect" .)