Vessels of the Royal Navy in America (4)
I believe the answer is:
urns
'vessels' is the definition.
(urn is a kind of vessel)
'royal navy in america' is the wordplay.
'royal navy' becomes 'RN' (abbreviation for Royal Navy).
'in' is an insertion indicator.
'america' becomes 'US' (United States).
'rn' inserted into 'us' is 'URNS'.
'of the' is the link.
(Other definitions for urns that I've seen before include "Runs to get large vases" , "Large containers for tea" , "Vase-shaped vessels" , "Vessels to hold the ashes of the dead" , "Runs to get funeral vases" .)