  We study the category of finite--dimensional representations for a basic
classical Lie superalgebra $\Lg=\Lg_0\oplus \Lg_1$. For the ortho--symplectic
Lie superalgebra $\Lg=\mathfrak{osp}(1,2n)$ we show that certain objects in
that category admit a fusion flag, i.e. a sequence of graded
$\Lg_0[t]$--modules such that the successive quotients are isomorphic to fusion
products. Among these objects we find fusion products of finite--dimensional
irreducible $\Lg$--modules, truncated Weyl modules and Demazure type modules.
Moreover, we establish a presentation for these types of fusion products in
terms of generators and relations of the enveloping algebra.
