Tension for saint about ship (6)
I believe the answer is:
stress
'tension' is the definition.
(I know that tension can be written as stress)
'saint about ship' is the wordplay.
'saint' becomes 'st' (abbreviation).
'about' becomes 're' (regarding).
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'st'+'re'+'ss'='STRESS'
'for' acts as a link.
(Other definitions for stress that I've seen before include "'Worry, pressure (6)'" , "'Strain, tension (6)'" , "possible excuse for sickie?" , "what causes tension" , "State mental or emotional strain" .)