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orxClock_AddTimer(orxClock_FindFirst(orx2F(-1.0f), (void *StartEnemyWave)(orxClock_GetInfo(orxClock_FindFirst(orx2F(-1.0f)), ) ,orxConfig_GetListString("ListDelay", wave_delay)), 1, );
First of all, you don't need to cast your timer callback as long as its definition is compatible. The last parameter, context, is simply a value we'll then transmit to your callback when we call it. If you don't need any context to be transmitted to your callback, then you can simply leave it to orxNULL.
Here's some code:
Note that in your exemple you were getting a string from config and not a float for your delay.