Cleaning iPhone 5 charging dock?

Is there any chance I can safely clean the inside of the charging slot on my phone? It's not debris or dust inside, it's hard to explain but there's black line smudgy stuff I guess it's from friction of putting it in and out.

Use clean spirit to clean it with cotton bud or spirit spray, after cleaning the connector d'not use for at-least 30minutes because spirit drying is be soon, but to ensure its completely dried,

first charge the phone completely after its fully charged u start cleaning so that for next couple of hours you will not be needing the charger