Can a non-solicitation clause stop a seller from poaching suppliers, not just staff or customers?

Yes, if the clause is drafted to include suppliers, since non-solicitation covenants are not limited by law to only employees or customers — their scope is purely a matter of how the specific clause is written. Where supplier relationships are genuinely important to the value of the business being purchased, for example a business built around a small number of key supply arrangements, buyers commonly negotiate a supplier non-solicitation or non-interference provision alongside the more familiar employee and customer non-solicit clauses.

Such a clause typically restricts the seller from soliciting the business's suppliers or vendors to end or reduce their relationship with the business, or to instead deal with a competing venture the seller starts or joins. Whether this kind of protection exists in a given deal depends entirely on whether the parties identified supplier relationships as a specific risk worth addressing during negotiation, since it is not automatically included just because employee or customer non-solicitation clauses are present. A buyer for whom supplier continuity is genuinely important should raise this specifically rather than assuming it is already covered.