Essential subgroup for a fusion system

Definition
Suppose $$P$$ is a group of prime power order and $$\mathcal{F}$$ is a fusion system on $$P$$. A subgroup $$Q$$ of $$P$$ is termed a $$\mathcal{F}$$-essential subgroup of $$P$$ if it is $$\mathcal{F}$$-centric and if $$\operatorname{Aut}_{\mathcal{F}}(Q)/\operatorname{Aut}_Q(Q)$$ has a strongly p-embedded subgroup.