At the risk of sounding obnoxious, the only clip an SKS has would be a stripper clip. The part I assume you're referring to is the magazine.
That being said, I'm not sure I understand the "snap in" part of your question, due to the fact that a Yugo SKS (and 90% of other SKS's) has a fixed magazine that really only gets opened while cleaning or to facilitate dumping the unfired rounds to unload the rifle.
Unless, of course, your SKS has had some modifications that allow it to use a removable magazine of one type or another.
If this is the case, then you should be sure that it was done in compliance with 18 USC 922r so you don't get jammed up over something you didn't do, or didn't know about.
THEN you can fix what's broken...

922 (r)
The Imported Parts Law(1990)
178.39 otherwise known as 922(r) 10 Foreign parts law on semiauto Rifles & Shotguns
http://www.atf.treas.gov/regulations/27cfr178.htmlSec. 178.39 Assembly of semiautomatic rifles or shotguns.
(a) No person shall assemble a semiautomatic rifle or any shotgun using more than 10 of the imported parts listed in paragraph (c) of this section if the assembled firearm is prohibited from importation under section 925(d)(3) as not being particularly suitable for or readily adaptable to sporting purposes.
(b) The provisions of this section shall not apply to:
(1) The assembly of such rifle or shotgun for sale or distribution
by a licensed manufacturer to the United States or any department or agency thereof or to any State or any department, agency, or political subdivision thereof; or
(2) The assembly of such rifle or shotgun for the purposes of
testing or experimentation authorized by the Director under the
provisions of Sec. 178.151; or
(3) The repair of any rifle or shotgun which had been imported into or assembled in the United States prior to November 30, 1990, or the replacement of any part of such firearm.
(c) For purposes of this section, the term imported parts are:
(1) Frames, receivers, receiver castings, forgings or stampings
(2) Barrels
(3) Barrel extensions
(4) Mounting blocks (trunions)
(5) Muzzle attachments
(6) Bolts
(7) Bolt carriers
(8 ) Operating rods
(9) Gas pistons
(10) Trigger housings
(11) Triggers
(12) Hammers
(13) Sears
(14) Disconnectors
(15) Buttstocks
(16) Pistol grips
(17) Forearms, handguards
(18) Magazine bodies
(19) Followers
(20) Floorplates
I'd say #36 is causing your problem.
http://www.e-gunparts.com/schemzoom.asp?schem=2620z59-66