Fancy garlic, perhaps? This may have gone off with exposure (9)
I believe the answer is:
flashbulb
'this may have gone off with exposure' is the definition.
(as in flash photography)
'fancy garlic perhaps?' is the wordplay.
'fancy' becomes 'flash' (flash can mean special or ostentatious).
'garlic perhaps?' becomes 'bulb' (garlic is a type of bulb).
'flash'+'bulb'='FLASHBULB'
(Other definitions for flashbulb that I've seen before include "It may help photograph" , "Old camera attachment" , "something generating red eyes?" .)