Notices container aboard steamship (5)
I believe the answer is:
spots
'notices' is the definition.
(spot can mean to notice or see)
'container aboard steamship' is the wordplay.
'container' becomes 'pot' (pot is a kind of container).
'aboard' means one lot of letters goes inside another.
'steamship' becomes 'ss' (nautical abbreviation).
'pot' going within 'ss' is 'SPOTS'.
(Other definitions for spots that I've seen before include "Blemishes" , "Catches sight of" , "Picks out" , "Acne" , "Result of outbreak, possibly" .)