Almost destroy the right lung (8)
I believe the answer is:
breather
But I can't explain it at all! Could you help me understand?
(Other definitions for breather that I've seen before include "Short rest break" , "lung, possibly?" , "An informal break - inhale and exhale" , "Rather be having a rest - inhale" , "Informally a pause for rest - or to take in air" .)