Picture held up by popular umpire (5)
I believe the answer is:
mural
'picture' is the definition.
(mural is a kind of picture)
'held up by popular umpire' is the wordplay.
'up by' says the letters should be written backwards.
'held' says the answer is hidden in the clue.
'larum' is hidden within 'popular umpire'.
'larum' reversed gives 'MURAL'.
(Other definitions for mural that I've seen before include "Wall design" , "Artwork" , "Wall art" , "Large wall painting" , "Drawing on a wall" .)