This achievement requires you to get a non-loan Master Icon in HUT.
Master Icons are players from back in the day, and you can tell them by their distinct blue/grey card design. Below is an example one I have:
There are a few ways you can earn Master Icon card:
-Unlock them in packs (most if not all packs have a <1% chance of having a Master Icon in them.
-Trade in x Monthly Collectibles earned in daily/weekly challenges, HUT event challenges, and daily packs and trade these in for 1 Icon Collectible (amount varies from month to month)
-Trade in 50 Gold Players for 1 Icon Collectible.
-Trade in 2 Gold Collectibles for 1 Icon Collectible.
-Complete all HUT milestone challenges in one category for Icon Collectibles
The easiest thing to do in my opinion is to trade in 50 gold players for 1 Icon Collectible. You can then trade in this collectible for an 85 Overall Master Icon.
The easiest way to earn Gold Players are by playing Squad Battles. If you play enough you'll end up with a decent ranking and will get a fair amount of packs containing gold players.
Another way to earn gold players is to go to Exchange > Sets > Upgrade Sets and you can trade in 8 silver players for 2 gold players. You get two silver players a day from daily packs.
Once you've accumulated your gold players, Go to Exchange > Sets > Icon Sets and select the Gold Players to Icons Collectible set. You can fill this in by individually selecting players you want to trade in, but if you don't care about the gold players you're trading in, you can just click the left stick to auto fill and it will fill the set with any gold players not on any lineups. Once it's filled, hit Y to complete the set and you'll have to go to the Store to grab your icon collectible.
Once you have your icon collectible, go back to the Icon Sets and and choose 85 OVR Silver Master Icon Choice, auto fill the slot and complete the set. Choose any Master Icon you want and achievement unlocked.
*Note: Leigrez has mentioned that buying a master icon from the auction house didn't pop the achievement. I wouldn't recommend doing this anyways as master icons in the auction house are normally incredibly overpriced, but if you do decide that's what you want to do, be warned you may not unlock the achievement.
Lately, I've also seen Silver Icon HUT packs in the store rather frequently. For 125,000 coins (or some sort of equivalent of the hockey tokens or whatever they're called that you can spend real money on), you can get a guaranteed Silver Master Icon plus a few other cards. Just another option if you see the pack in the store and have the money, but I cannot guarantee this will work or not (I'd assume it should though).
*EDIT* It looks like you can also earn icon collectibles by completing weekly challenges now. This is by far the easiest way to do this so I would highly suggest using this method. They normally consist of opening daily packs, completing challenges, sets, shot totals, etc. I believe if you hit Right Trigger on the HUT menu it will bring up your challenges.