Sonnet king composed in part of London (10)
I believe the answer is:
kensington
'part of london' is the definition.
(I've seen this before)
'sonnet king composed' is the wordplay.
'composed' indicates an anagram.
'sonnet'+'king'='sonnetking'
'sonnetking' with letters rearranged gives 'KENSINGTON'.
'in' acts as a link.
(Other definitions for kensington that I've seen before include "neighbour of Chelsea" , "Royal Albert Hall area" , "part of London" , "London palace" , "Royal Albert Hall location" .)