Run-down lake's charm spoiled (10)
I believe the answer is:
ramshackle
'run-down' is the definition.
(thesaurus)
'lake's charm spoiled' is the wordplay.
'spoiled' indicates anagramming the letters.
'lakes'+'charm'='lakescharm'
'lakescharm' anagrammed gives 'RAMSHACKLE'.
(Other definitions for ramshackle that I've seen before include "Badly-organised" , "Dilapidated" , "Rickety - derelict" , "Decrepit" , "In severe disrepair" .)