GBA Slot Cover | Nintendo DS Lite | Support | Nintendo UK
The DS slot is too slow to reasonably run GBA games so you will either need a so called enhanced flash cart there (which for most means Supercard DSTwo) or a GBA slot/slot 2 cart.
Game Boy Advance - Game Boy/GBA/DS Compatability FAQ - Game Boy ...
If you are playing on a DS Lite, the GBA cartridge will jut out of the second slot. Do not force it in; this is how it's supposed to fit.
GBA Slot Cover | Nintendo DS Lite | Support | Nintendo UK
The Nintendo DS Lite slot cover is enclosed in the original Nintendo DS Lite packaging and is used to protect Slot-2 for Game Boy Advance games.
Nintendo DS - Wikipedia
[9] On March 2, 2006, Nintendo launched the Nintendo DS Lite, a slimmer and lighter redesign of the original Nintendo DS with brighter screens and a longer lasting battery.