Leader recalled agent in capital city (7)
I believe the answer is:
emperor
'leader' is the definition.
(I've seen this before)
'recalled agent in capital city' is the wordplay.
'recalled' is a reversal indicator (to recall can mean to bring something back).
'agent' becomes 'rep' (short for representative).
'in' means one lot of letters goes inside another.
'capital city' becomes 'Rome' (capital of Italy).
'rep' going into 'rome' is 'rorepme'.
'rorepme' back-to-front is 'EMPEROR'.
(Other definitions for emperor that I've seen before include "A moth; a penguin" , "Powerful ruler" , "Purple --; -- penguin" , "Tsar" , "Napoleon Bonaparte, for instance" .)