Follow this structure for your competency answer:
The interviewers need to understand about the context to help them in judging your actions and the outcome. This should be as brief as you can make it - some candidates explain far too much about the industry or organisation or section, while not spending enough time talking about what they have actually done.
The actions you outline allow the interviewers to match your experience to the definition of the competency and the requirements of the new role. This section should be the longest. Make sure you keep the competency in mind and use the example to demonstrate evidence of the competency.
The outcome or results of your actions give the interviewers some indication of the contribution you made, the impact your work had and the quality of your work.
The same advice about this structure of an answer applies when completing a public sector application form that asks you to answer competency questions on the form.