The most common and most likely answer to this crossword clue is the 7 plus 4 plus 4 letter word NOTTING HILL GATE
I've seen this crossword clue in The Sunday Telegraph
N
O
T
T
I
N
G
H
I
L
L
G
A
T
E
More clues leading to the result NOTTING HILL GATE
Buddy explains!
The straight part
We know that "part of London" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case part of london = notting hill gate.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.