Sailor to achieve goal (6)
I believe the answer is:
target
'goal' is the definition.
(target is a kind of goal)
'sailor to achieve' is the wordplay.
'sailor' becomes 'tar' (term for a sailor).
'to achieve' becomes 'get' (I've seen this in another clue).
'tar'+'get'='TARGET'
(Other definitions for target that I've seen before include "Point to aim at (6)." , "One aimed at" , "aunt Sally" , "Aim of an attack" , "Thing aimed at" .)