Drone in America having completed miles (5)
I believe the answer is:
thrum
'drone in america' is the definition.
'thrum' can be an answer for 'drone' (I've seen this before). I am not sure about the 'in america' bit.
'completed miles' is the wordplay.
'completed' becomes 'thru' (I can't explain this - if you can you should give a lot more credence to this answer).
'miles' becomes 'm' (common abbreviation).
'thru'+'m'='THRUM'
'having' acts as a link.
Can you help me to learn more?
(Other definitions for thrum that I've seen before include "Drone; tap idly" , "bit of thread" , "Drum with fingers - bits of coarse yarn" , "Continuous rhythmic humming sound" , "Strum; thread end" .)