Bleak possibility for an old sailor (5)
I believe the answer is:
blake
'an old sailor' is the definition.
The definition suggests a singular noun which matches the answer.
'bleak possibility' is the wordplay.
'bleak' can be anagrammed to 'BLAKE'.
But, I'm unsure how the anagram is indicated.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for blake that I've seen before include "William -, English poet, artist and visionary" , "William -, (Jerusalem)" , "English poet and artist, d. 1827" , "Songs of Innocence poet" , "Exposed (to the air)" .)