  Cross-connection theory propounded by K. S. S. Nambooripad describes the
ideal structure of a regular semigroup using the categories of principal left
(right) ideals. A variant $\mathscr{T}_X^\theta$ of the full transformation
semigroup $(\mathscr{T}_X,\cdot)$ for an arbitrary $\theta \in \mathscr{T}_X$
is the semigroup $\mathscr{T}_X^\theta= (\mathscr{T}_X,\ast)$ with the binary
operation $\alpha \ast \beta = \alpha\cdot\theta\cdot\beta$ where $\alpha,
\beta \in \mathscr{T}_X$. In this article, we describe the ideal structure of
the regular part $Reg(\mathscr{T}_X^\theta)$ of the variant of the full
transformation semigroup using cross-connections. We characterize the
constituent categories of $Reg(\mathscr{T}_X^\theta)$ and describe how they are
\emph{cross-connected} by a functor induced by the sandwich transformation
$\theta$. This lead us to a structure theorem for the semigroup and give the
representation of $Reg(\mathscr{T}_X^\theta)$ as a cross-connection semigroup.
Using this, we give a description of the biordered set and the sandwich sets of
the semigroup.
