1. To cause an effect on; influence.
A heavy diet of television drama played on his feelings.
2. To work upon for a planned effect; excite to a desired action by cunning plans; manage.
The makeup salesman played on the woman's wish to look beautiful.
In some places, leaders play upon people's superstitious fears.
He played on the man's ambition and love of honor.
Source: A Dictionary of American Idioms