Waffle iron held up window (5)
I believe the answer is:
oriel
'window' is the definition.
(oriel is a type of window)
'waffle iron held up' is the wordplay.
'held' says the answer is hidden in the clue.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'leiro' is hidden in the letters of 'waffle iron'.
'leiro' written backwards gives 'ORIEL'.
(Other definitions for oriel that I've seen before include "Protruding window" , "English college" , "Projecting window in upper storey" , "Upper-story bay window" , "Recessed bay window" .)