Colossal vessel contains ointment (5)
I believe the answer is:
salve
'ointment' is the definition.
(I know that ointment can be written as salve)
'colossal vessel contains' is the wordplay.
'contains' indicates a hidden word.
'SALVE' is hidden within 'colossal vessel'.
(Other definitions for salve that I've seen before include "Greeting in Rome" , "Relieve - ointment" , "Something that soothes" , "Ointment from the vales" , "Save - ointment" .)