Vessel of little weight giving warning at sea? (9)
I believe the answer is:
lightship
'vessel' is the definition.
(lightship is a kind of vessel)
'of little weight giving warning at sea?' is the wordplay.
'of little weight' becomes 'light' (I've seen this before).
'giving warning at sea?' becomes 'ship' (I can't explain this - if you can you should believe this answer much more).
'light'+'ship'='LIGHTSHIP'
Can you help me to learn more?
(Other definitions for lightship that I've seen before include "vessel anchored near rocks?" , "Pilot's guide" , "Guiding vessel sounds as if it has no cargo" , "Moored vessel warning sailors of a hazard" , "Navigational aid" .)