Instruments for measure leadership competency is different in each organization. Organization in Academy environment needs teacher leadership, an Industrial environment will need a middle leadership, distributed leadership, and instructional leadership. Although leadership is an art which works in different person.

Thank you Sir.....

What are the best construct to develop and validate instrument to measure head science subject leader competencies?

Think those leaderships you mentioned in your question above can underpin on common leadership theories / styles that you can easily find from leadership books (see some examples in diagram attached). Perhaps what you can do is - perform rigorous literature review on those common theories & adapt to specific leadership construct that you try to develop / enhance.

Likewise for leadership instrument that you try to develop / enhance, you can refer to this RG link for some examples that you can start with:

https://www.researchgate.net/post/Can_anyone_recommend_an_instrument_for_measuring_leadership_skills

Thank you very much Sir for your suggestion... i'm very appriciate your recommended... thanks again