Some sailors suffer (3)
I believe the answer is:
ail
'suffer' is the definition.
(ailing is a kind of suffering)
'some sailors' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'AIL' is hidden within 'sailors'.
(Other definitions for ail that I've seen before include "Cause to feel indisposed" , "pain" , "Be unwell, suffer" , "Be in poor health" , "Afflict -- feel unwell" .)