Clue: Object about island starting to make drone (9)
Answer: THRUMMING
Explanation: Definition: drone
 THING(an object that one cannot or does not wish to give a specific name to) **containing**(about) [ RUM(an island in the Inner Hebrides, Scotland) + **1st letter of**(starting to) "make" ].
Defn: …/a continuous low humming sound.