City bores showing skill in desert (6)
I believe the answer is:
defect
'desert' is the definition.
(I know that desert can be written as defect)
'city bores showing skill' is the wordplay.
'city' becomes 'EC' (the City of London postcode).
'bores' is an insertion indicator (to bore something can mean to drill into it).
'showing skill' becomes 'deft'.
'ec' placed inside 'deft' is 'DEFECT'.
'in' acts as a link.
(Other definitions for defect that I've seen before include "Shortcoming" , "Lack" , "Fault - default" , "Leave the country" , "mistake" .)