Weightlifter single sailor upset (5)
I believe the answer is:
atlas
'weightlifter' is the definition.
(I have seen 'Legendary weightlifter' mean 'atlas' so perhaps 'weightlifter' could also mean 'atlas')
'single sailor upset' is the wordplay.
'single' becomes 'a'.
'sailor' becomes 'salt' (salt is a kind of sailor).
'upset' says the letters should be written backwards.
'salt' reversed gives 'tlas'.
'a'+'tlas'='ATLAS'
(Other definitions for atlas that I've seen before include "It appears at the top of the spine" , "Holder of world" , "Size of paper once" , "Titan who supported the heavens" , "Book of maps - fifteenth satellite of Jupiter" .)