Try this:
FIELD-SYMBOLS: <fs_matnr> TYPE any.
TYPES: BEGIN OF ty_test,
matnr TYPE matnr,
END OF ty_test.
DATA: li_test TYPE STANDARD TABLE OF ty_test,
wa_test TYPE ty_test.
LOOP AT <fs_it_output> ASSIGNING <fs_wa_output>.
ASSIGN COMPONENT of 'MATNR' OF STRUCTURE <fs_wa_output> to <fs_field>.
MOVE <fs_matnr> TO wa_test-matnr.
APPEND wa_test TO li_test.
ENDLOOP.