Nile choppy for royal vessel (5)
I believe the answer is:
liner
'vessel' is the definition.
(I know that liner is a type of passenger ship)
'nile choppy for royal' is the wordplay.
'choppy' is an anagram indicator.
'for' is a charade indicator (letters next to each other).
'royal' becomes 'r' (abbreviation).
'nile' anagrammed gives 'line'.
'line'+'r'='LINER'
(Other definitions for liner that I've seen before include "Commercial ship" , "cover for interior" , "QE2, perhaps" , "Large passenger or cargo ship travelling on regular route" , "Passenger transport" .)