duty-bound
adjective /ˌdjuːti ˈbaʊnd/
  /ˌduːti ˈbaʊnd/
[not before noun] (formal)- having to do something because it is your duty责无旁贷;义不容辞 - I felt duty-bound to help him.我觉得帮助他责无旁贷。 
- I felt in duty bound to report the incident.我觉得报道这一事件对我来说是义不容辞的。 
 
- I felt duty-bound to help him.