Penny leaving store to tour old London area (4)
I believe the answer is:
soho
'london area' is the definition.
(I've seen this before)
'penny leaving store to tour old' is the wordplay.
'penny leaving store' becomes 'sho' (I am not sure about this - if you are sure you should believe this answer much more).
'to tour' indicates putting letters inside (to tour can mean to go around).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'sho' placed around 'o' is 'SOHO'.
(Other definitions for soho that I've seen before include "London square" , "capital district" , "W London area" , "London district known for its nightlife" , "Parts of London and New York City with the same name" .)