Briefly attempt to restrict dictator’s power (7)
I believe the answer is:
stamina
'power' is the definition.
(I've seen this before)
'briefly attempt to restrict dictator's' is the wordplay.
'briefly' means to remove the last letter.
'attempt to' becomes 'stab' (I've seen this before).
'restrict' is an insertion indicator.
'dictator' becomes 'amin' (Idi Amin, Ugandan dictator).
'stab' with its final letter taken off is 'sta'.
'sta' enclosing 'amin' is 'STAMINA'.
(Other definitions for stamina that I've seen before include "Endurance, strength to stay the course" , "capacity to endure" , "Endurance - staying power" , "perseverance" , "toughness in > male parts" .)