Check traveller getting on ship (7)
I believe the answer is:
repress
'check' is the definition.
(I've seen this before)
'traveller getting on ship' is the wordplay.
'traveller' becomes 'rep' (travel company worker).
'getting' says to put letters next to each other.
'on' becomes 're' ('on' can be mean 'with reference to').
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'rep'+'re'+'ss'='REPRESS'
(Other definitions for repress that I've seen before include "Forcibly keep down" , "Curb" , "Check" , "Silence" , "Put in irons, maybe" .)