City, then Hearts, finally beat Real (4)
I believe the answer is:
echt
'real' is the definition.
(I've seen this in another clue)
'city then hearts finally beat' is the wordplay.
'city' becomes 'EC' (the City of London postcode).
'then' is a charade indicator (letters next to each other).
'hearts' becomes 'h' (abbreviation used in card games e.g. bridge).
'finally' indicates one should take the final letters.
The last letter of 'beat' is 't'.
'ec'+'h'+'t'='ECHT'
(Other definitions for echt that I've seen before include "German's real" , "Genuine (Ger.)" , "Authentic (from German)" , "Genuine -- honest" , "Genuine - authentic" .)