Duty of force in charge close to palace (6)
I believe the answer is:
office
'duty' is the definition.
(office is a kind of duty)
'of force in charge close to palace' is the wordplay.
'force' becomes 'f' (symbol used in Physics e.g. f=ma).
'in charge' becomes 'ic'.
'close to' suggests the final letters (the close/ending of).
The last letter of 'palace' is 'e'.
'of'+'f'+'ic'+'e'='OFFICE'
(Other definitions for office that I've seen before include "Post - bureau" , "Post - place of work" , "Position, or building in which colours in layers" , "Administrative unit" , "Business room - position of responsibility or duty" .)