The only problem I see is the Left recursion.
Therefore the new grammar would be
$S\rightarrow \left ( L \right )|a$
$L\rightarrow SL'$
$L'\rightarrow .SL' | \epsilon$
$-----------------------------------$
FT( S)={( ,a }
FT( L)={ ( ,a}
FT( L' )={ .,$\epsilon$}
FL( S)={ $,.,( ,a }
FL( L)={ )}
FL( L')={ ) }