Burning bridges, e.g. (5)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
arson
(Other definitions for arson that I've seen before include "Fire requiring forensic study" , "Fire-raiser's crime" , "Crime of fire-setting (5)" , "Sonar (anag.)" , "Malicious burning to destroy property" .)