Cast has Romeo in short hairpiece (6)
I believe the answer is:
troupe
'cast' is the definition.
(I've seen this before)
'romeo in short hairpiece' is the wordplay.
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'in' means one lot of letters goes inside another.
'short' means to remove the last letter.
'hairpiece' becomes 'toupee' (toupee is a kind of hairpiece).
'toupee' with its final letter removed is 'toupe'.
'r' inserted inside 'toupe' is 'TROUPE'.
'has' acts as a link.
(Other definitions for troupe that I've seen before include "Theatre company" , "Company of dancers" , "Travelling company of actors" , "Cast" , "travelling band" .)