unfortunately not, Karlos.
The Amiga port doesn't supply Y-C output (exept CD32 and/or CDTV don't remember now).
An easy way to achieve an Y-C output from an Amiga RGB port, is an encoder or a modded (crap) A520 or, if you can find one, a cheap YC genlock (with pass-trough option).
I said with a pass-through switch, because an "always active" genlock, may cause troubles in some configuration/enviroments.
EDIT- i meant to say "by pass" switch instead of "passthrough" (that is a common feature in about all gelocks)