When you take this feat, select one weapon or attack type. You gain advantage 1 per tier of this feat for any damaging attack made with your chosen attack type. This bonus does not apply to bane attacks or boon invocations. Examples of attack types you can choose to specialize in include fire, cold, lightning, acid, poison, entropy, and force - though this list is not exhaustive.
So potentially yes, but keep in mind this depends very much on the character, setting and the GM. Entropy might mean shadow magic, poisons or necromancy in a generic fantasy setting, so it would be reasonable that Attack Specialisation only applies to one of these, as they are rather distinct from each other. But in the end this should be worked out between a player and the GM.