Strand that's brownish crimson (6)
I believe the answer is:
maroon
I believe this clue is a double definition.
'strand' is the first definition.
(synonyms)
'brownish crimson' is the second definition.
(I've seen this before)
'that's' is the link.
(Other definitions for maroon that I've seen before include "Could be a warning signal" , "Dark crimson" , "Slaves' descendant" , "Brownish-crimson - abandon ashore" , "Leave stranded with little hope of rescue" .)