Dance round trailer? (5)
I believe the answer is:
promo
'trailer?' is the definition.
(I've seen this in another clue)
'dance round' is the wordplay.
'dance' becomes 'prom' (prom is a kind of dance).
'round' becomes 'o' (round can mean a round object).
'prom'+'o'='PROMO'
(Other definitions for promo that I've seen before include "Brief publicity" , "Ad" , "publicity event" , "for [a] little while" , "Encouragement" .)