City in South Africa has leading private eye (4)
I believe the answer is:
'city' is the definition.
(Pisa is an example)
'south africa has leading private eye' is the wordplay.
'south africa has' becomes 'sa' (I can't justify this - if you can you should give a lot more credence to this answer).
'leading' means one lot of letters go next to another.
'private eye' becomes 'PI' (synonyms).
'sa' after 'pi' is 'PISA'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for pisa that I've seen before include "much-visited city" , "City in Tuscany" , "listed building site" , "Site of the famous leaning tower" , "There's a marked inclination here" .)