Wave from queen by posh car (not Sierra) (6)
I believe the answer is:
roller
'wave' is the definition.
(I know that roller is a type of wave)
'queen by posh car not sierra' is the wordplay.
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'by' is a charade indicator (letters next to each other).
'posh car' becomes 'rolls' (short for rolls royce).
'not' indicates named letters should be taken away.
'sierra' becomes 'S' (phonetic alphabet: alpha, bravo, charlie etc.).
'rolls' with 's' taken away is 'roll'.
'er' after 'roll' is 'ROLLER'.
'from' is the link.
(Other definitions for roller that I've seen before include "road maintenance vehicle" , "Heavy sea wave and hair curler" , "Cylinder for lawn etc" , "Swelling wave; bird" , "Long heavy wave approaching the shore" .)