A dream Sue reconstructed about queen's fancy-dress party (10)
I believe the answer is:
masquerade
'fancy-dress party' is the definition.
(as in a masquerade ball)
'a dream sue reconstructed about queen's' is the wordplay.
'reconstructed' indicates anagramming the letters.
'about' means one lot of letters goes inside another.
'queen' becomes 'q' (abbreviation for queen in chess).
'a'+'dream'+'sue'='adreamsue'
'adreamsue' is an anagram of 'masuerade'.
'masuerade' going around 'q' is 'MASQUERADE'.
(Other definitions for masquerade that I've seen before include "Dress up" , "Adam's queer? (anag)" , "where everyone's wearing the veil" , "Deception" , "Pretence - masked ball" .)