City hideaway serving up cake (6)
I believe the answer is:
eclair
'cake' is the definition.
(I've seen this before)
'city hideaway' is the wordplay.
'city' becomes 'ec' (the City of London postcode).
'hideaway' becomes 'lair' (I've seen this before).
'ec'+'lair'='ECLAIR'
'serving up' is the link.
(Other definitions for eclair that I've seen before include "Cake, "long in shape but short in duration"" , "Lacier (anag.)" , "Long chocolate cake for Claire" , "I clear off with thin chocolate cake" , "Choux pastry cream cake" .)