Same ship suffering stress (8)
I believe the answer is:
emphasis
'stress' is the definition.
('emphasis' can be a synonym of 'stress')
'same ship suffering' is the wordplay.
'suffering' is an anagram indicator.
'same'+'ship'='sameship'
'sameship' is an anagram of 'EMPHASIS'.
(Other definitions for emphasis that I've seen before include "Importance; priority" , "Stress or significance" , "Force" , "Stress - misshape (anag)" , "Intensity of expression" .)