In charge of manifest, briefly (4)
I believe the answer is:
over
'in charge of' is the definition.
(eg a manager works over other people)
'manifest briefly' is the wordplay.
'manifest' becomes 'overt' (I've seen this before).
'briefly' means to remove the last letter.
'overt' with its last letter removed is 'OVER'.
(Other definitions for over that I've seen before include "Passed" , "Period of play" , "Finished, done" , "See 12" , "Finished like bowling session" .)