Answer:

swallowtail

Answer	Crossword Clue
SWALLOWTAIL	Type of butterfly
SWALLOWTAIL	Butterfly.
SWALLOWTAIL	Coat for the opera

SWALLOWTAIL	Part of a full-dress suit
SWALLOWTAIL	Capistrano copper?

Crossword

a puzzle consisting of a grid of squares and blanks into which words crossing vertically and horizontally are written according to clues.