Serenade knight after king in French palace (10)
I believe the answer is:
kensington
'palace' is the definition.
(I've seen this before)
'serenade knight after king in french' is the wordplay.
'serenade' becomes 'singto'.
'knight' becomes 'n' (chess).
'after' says to put letters next to each other.
'king' becomes 'k'.
'in french' becomes 'en' ('en' can be French for 'in' e.g. en France).
'singto'+'n'='sington'
'k'+'en'='ken'
'sington' after 'ken' is 'KENSINGTON'.
(Other definitions for kensington that I've seen before include "Royal Albert Hall area" , "London palace" , "neighbour of Chelsea" , "London district" , "Royal Albert Hall location" .)