Without sparkle (4)
(Other definitions for flat that I've seen before include "Apartment - on the level" , "Even - somewhere to live" , "Punctured tyre" , "No longer charged" , "lacking in taste" .)
(Other definitions for drab that I've seen before include "Cheerless, colourless" , "Drearily dull; slattern" , "Dull, uninteresting" , "kind of tart" , "Dowdy" .)