Someone (mag-) keeps a spare, reserves, sets aside something (i-) for someone (-an).
Magrisīrba ako so bombilya no linti ko do kammyanaya.
I keep a spare of my flashlight bulb for monsoon season.
Irisīrba mo asaya bolpin mo, ta dēkey danaya kanen asaya.
Reserve one of your ballpoint pens, because the ink [Lit. 'the food'] in the one is already little.
Risīrbaan mo yaken so laylay ko.
Reserve a shirt for me.