Star in The King and I, classy lass (5)
I believe the answer is:
rigel
'star' is the definition.
(star in the constellation Orion)
'king and i classy lass' is the wordplay.
'king' becomes 'R' (abbreviation for rex, king in Latin).
'and' says to put letters next to each other.
'classy lass' becomes 'gel' (term for an upper-class young woman).
'r'+'i'+'gel'='RIGEL'
'in the' is the link.
(Other definitions for rigel that I've seen before include "Orion's brightest star" , "shiner" , "Brightest star in Orion" .)