explain away
To try to minimize a problem or issue through explanation. A noun or pronoun can be used between "explain" and "away." He's trying to explain it away, but I know he lied to me.
explain something away
to explain something so that it is no longer a problem. You can try to explain it away if you want, but that won't solve the problem. You can't just explain away all your problems.
explain away
Dismiss or minimize the importance of something, especially something detrimental. For example, "His words were taken down, and though he tried to explain them away, he was sent to the Tower" (Thomas Macaulay, The History of England, 1855). [c. 1700]
explain away
v. To dismiss or minimize the significance of something by explanation: The candidate tried to explain his earlier misstatements away. The researcher explained away the criticisms that were raised against her hypothesis.