Good government producing royal vessel (10)
I believe the answer is:
statecraft
'good government' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'royal vessel' is the wordplay.
'royal' becomes 'state' (I can't explain this - if you can you should give a lot more credence to this answer).
'vessel' becomes 'craft' (synonyms).
'state'+'craft'='STATECRAFT'
'producing' is the link.
Can you help me to learn more?
(Other definitions for statecraft that I've seen before include "required for government business" , "ministers need" , "Skilful management of national affairs" , "Political skill" , "Diplomacy" .)