Site around area in Kensington, for one (6)
I believe the answer is:
palace
'kensington for one' is the definition.
(Kensington Palace is an example)
'site around area in' is the wordplay.
'site' becomes 'place' (synonyms).
'around area' becomes 'a' (maths abbreviation. I am not sure about the 'around' bit.).
'in' means one lot of letters goes inside another.
'place' going around 'a' is 'PALACE'.
(Other definitions for palace that I've seen before include "Grand building" , "large house" , "Locality round a monarch's official residence" , "Regal mansion" , "Stately mansion" .)