I have a variable name in Bash as:
var=(any_word)_SuSE_11_design_guides
x=$(echo "$var" | some operation)
echo $x
SuSE_11_design_guides
_
I think you meant retain Everything behind first _ , which can be achieved using parameter-expansion.
string="(anyword)_SuSE_11_design_guides"
printf "%s\n" "${string#*_}"
SuSE_11_design_guides