Solve the puzzle the same way that you'd solve a numeric sudoku. Each of the letters A, E, F, G, I, L, N, R and S is found once in every row, column and 3×3 box. When you're done, copy the shaded squares in order from top to bottom, from left to right, to reveal the hidden word.

I
L
F
A
F
R
E
N
E
G
S
I
R
G
A
A
S
I
R
F
R
E
F
S
N
N
L
A
L
G
A
F