Distress signal to leave ashore? (6)
I believe the answer is:
maroon
I believe this clue is a double definition.
'distress signal' is the first definition.
(firework used as a warning)
'to leave ashore?' is the second definition.
(Other definitions for maroon that I've seen before include "Could be a warning signal" , "castaway?" , "Strand, isolate" , "distress signal" , "Reddish-brown" .)