Across the ship there's a smile (5)
I believe the answer is:
abeam
'across the ship' is the definition.
(nautical term)
'there's a smile' is the wordplay.
'there's' says to put letters next to each other.
'smile' becomes 'beam' (beam can mean to smile).
'a' put next to 'beam' is 'ABEAM'.
(Other definitions for abeam that I've seen before include "To the right or left of the centre of the ship" , "Position relative to ship" , "In a line at right angles to a vessel's length" , "angled across the plane" , "The way sailor goes across ship" .)