Performer, one sensible about places like London, not half (10)

'performer' is the definition.
(recitalist is a kind of performer)

'one sensible about places like london not half' is the wordplay.
I cannot quite see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
'about' could be 're' ('re' means regarding or about) and 're' is found within the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?