Sound pleased, turning up with a posh car (4)
I believe the answer is:
purr
'sound pleased' is the definition.
(I've seen this in other clues)
'turning up with a posh car' is the wordplay.
'turning' says the letters should be written in reverse.
'with' says to put letters next to each other.
'a posh car' becomes 'rr' (short for Rolls Royce).
'up' in reverse letter order is 'pu'.
'pu'+'rr'='PURR'
(Other definitions for purr that I've seen before include "content? I might" , "Sound of happy animal" , "Appreciative feline sound" , "Cat noise" , "Tiddles' sound" .)