The phrase "slight challenge" means a small difficulty or obstacle that is not very significant, but still requires some effort to overcome. Full definition
The only slight challenge with cookies made with coconut oil is the dough tends to get soft after working with it and it warms up to room temp. (veggieandthebeastfeast.com)
The only slight challenge can be finding a green pistachio ice cream, since many brands only come in white, but Thrifty makes one! (marthastewart.com)
The gospel is determinedly set against what the paper views as «deadly sins,» such as religious certainty, almost any kind of conservatism, the Second Amendment, and even the slightest challenge to the unlimited abortion license. (firstthings.com)