Saint on about ship showing strain (6)
I believe the answer is:
stress
'strain' is the definition.
(I know that stress is a type of strain)
'saint on about ship' is the wordplay.
'saint' becomes 'st' (abbreviation).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'about' becomes 're' (regarding).
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'st'+'re'+'ss'='STRESS'
'showing' is the link.
(Other definitions for stress that I've seen before include "what causes tension" , "'Strain, tension (6)'" , "Emphasize" , "Force" , "Draw attention to" .)