Mysterious sailor's right about end of albatross (8)
I believe the answer is:
abstruse
'mysterious' is the definition.
(thesaurus)
'sailor's right about end of albatross' is the wordplay.
'sailor's' becomes 'abs' (abbreviation for able seaman).
'right' becomes 'true' ('true' is associated in meaning with 'right'**).
'about' is an insertion indicator.
'end of' says to take the final letters.
The last letter of 'albatross' is 's'.
'true' enclosing 's' is 'truse'.
'abs'+'truse'='ABSTRUSE'
(Other definitions for abstruse that I've seen before include "Esoteric" , "Incomprehensible to those with normal understanding" , "Hard to understand, recondite" , "Strange busts are difficult to understand" , "Hard to understand, complicated" .)