Pressing metal in the capital of Greece (7)
I believe the answer is:
'pressing' is the definition.
(ironing is a kind of pressing)
'metal in the capital of greece' is the wordplay.
'metal' becomes 'iron' (iron is a metal).
'the capital of' says to take the initial letters.
The initial letter of 'greece' is 'g'.
(Other definitions for ironing that I've seen before include "Pressing clothes" , "A housework chore" , "Making clothes smooth" , "having pressing business" , "Laundry job" .)