A backer is someone with a management position or equivalent title within a cannabis establishment.
From the law:
Section 1(2) "Backer" means any individual with a direct or indirect financial interest in a cannabis establishment. "Backer" does not include an individual with an investment interest in a cannabis establishment if (A) the interest held by such individual and such individual's spouse, parent or child, in the aggregate, does not exceed five per cent of the total ownership or interest rights in such cannabis establishment, and (B) such individual does not participate directly or indirectly in the control, management or operation of the cannabis establishment.