A deity in authority (4)
I believe the answer is:
thor
'a deity' is the definition.
(Thor is an example)
'in authority' is the wordplay.
'in' indicates a hidden word.
'THOR' is hidden within 'authority'.
(Other definitions for thor that I've seen before include "Imitative artistic work" , "Germanic thunder god; early US IRBM" , "Scandinavian thunder-god" , "Norse hammer-wielding god" , "One of the Norse gods" .)