Purple strand (6)
I believe the answer is:
maroon
I believe this clue is a double definition.
'purple' is the first definition.
(maroon is a purplish colour)
'strand' is the second definition.
(as in marooning someone on an island)
(Other definitions for maroon that I've seen before include "Dark crimson" , "Abandon (eg, on island)" , "Dark brownish-red" , "Brownish crimson" , "Isolate uncomfortably" .)