Filed from 2 published puzzles

DUMBER

Set to 2 different clues across 2 published puzzles, most often “Not so clever” — The New York Times, Monday, 12 September 1994.

6 letters

Every clue on record, most used first

Not so cleveronce
The New York Times — Monday, 12 September 1994
Not as brightonce
The New York Times — Saturday, 19 March 1994

Other answers to these clues

DENSER6 letters
DULLER6 letters
GLOOMIER8 letters
PALER5 letters