A small damage to a capital city (6)
I believe the answer is:
asmara
'capital city' is the definition.
'asmara' can be an answer for 'city' (I have seen 'African city' mean 'asmara' so perhaps 'city' could also mean 'asmara'). I am not sure about the 'capital' bit.
'a small damage to a' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'damage' becomes 'mar' (to mar is to spoil or damage).
'to' is a charade indicator (letters next to each other).
'a'+'s'+'mar'+'a'='ASMARA'
Can you help me to learn more?
(Other definitions for asmara that I've seen before include "Capital of Eritrea" , "African city" , "African capital" .)