Definitely! It'll probably even referment once it's cleared out as long as it's on the yeast cake - that's how responsive yeast are - is?
You need to add 0.7kg of DME to get around 5.4%. 0.5kg will give you 5%. Quantities are probably roughly the same if you're using beer enhancer.
If you get a 1kg bag, don't chuck it all in for the sake of it - get it where you want it, and keep the rest, it will almost definitely come in handy at some point!