Boat race hosts uncovered sordid hierarchy (13)
I believe the answer is:
subordination
'hierarchy' is the definition.
(thesaurus)
'boat race hosts uncovered sordid' is the wordplay.
I cannot really see how this works, but
'boat' could be 'sub' (submarine) and 'sub' is found within the answer.
'race' could be 'nation' (both can mean a national or ethnic group) and 'nation' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for subordination that I've seen before include "Inferiority of position or rank" , "Bending to authority" .)