### Clue: Feature of vessel on lake is excellent, excellent! (7)
### Answer: TOPSAIL 
 ### Explanation: Definition: Feature of vessel
 L(abbrev. for "lake") **placed below**(on … is, in a down clue) [TOPS(excellent/the best) + AI(A1/in the top grade/excellent, with the Roman numeral substitution)].
Defn:  …, a sailing ship, that is.