Part of Cairo, metropolitan capital (4)
I believe the answer is:
rome
'capital' is the definition.
(Rome is an example)
'part of cairo metropolitan' is the wordplay.
'part of' says the answer is hidden in the clue.
'ROME' can be found hidden inside 'cairo metropolitan'.
(Other definitions for rome that I've seen before include "European capital" , "Basis for cheese" , "Capital city" , "City not built in a day" , "Spanish Steps city" .)