Shifter play when in gear

[NiSMo]

Hey list. My shifter has started develop a lot of movement when in gear.
It's making it really hard to shift quickly accurately. My question is
that is this something that I can adjust or do I have to replace certain
components in my tranny. The amount of play the shifter has when in gear
amounts to almost 2 inches. It's gotten so bad that when I shift to
reverse the back up lights die if I push the shifter to the right (away
from me) when in gear.
A quick search in the archives yielded no results. Any input would be
appreciated. TIA.

Mark