According to Black formula , a vanila fx call option's pricing is
$$C(F,\tau) = D[N(d_+)F - N(d_-)K]$$ , where $\tau$ is the time to expiry, $D =e^{-r\tau}$ the discount factor, $F=S/D$ the outright forward rate, and $d_\pm =\frac{1}{\sigma\sqrt{\tau}}\left[\ln\frac{F}{K}\pm\frac12\sigma^2\tau\right]$.
If we look at the forward delta , it's $$\frac{\partial C}{\partial F}=DN(d_+)$$
Can I interprete that, with such an option shorted, if there's a outright forward rate deal at the same maturity, with $N(d_+)$ unit of currency 1, and $-N(d_-)F$ unit of currency 2, the delta will be fully hedged? Of course the ratio $\frac{N(d_-)}{N(d_+)}F$ is not at-the-money, but never mind that.