Answer:
a trait that gives an organism a reproductive advantage in the current environment
Step-by-step explanation:
An adaptation is a trait that provides an advantage to the individual in which it is present by making the individual more adaptable to its environment and as the result, the individual survive to reproductive age and able to produce more offspring than less adapted individual of its population.
So the trait gives an individual or organism a reproductive advantage in the current environmental situation. The trait or allele that helps in adaptation comes due to mutation or variation from meiosis or gamete fusion.