Bulb could be lit up (5)
I believe the answer is:
'bulb' is the definition.
(I've seen this before)
'could be lit up' is the wordplay.
'could be' indicates an anagram.
'litup' anagrammed gives 'TULIP'.
(Other definitions for tulip that I've seen before include "cause of mania once", "Spring bulb", "Spring-blooming plant", "Plant, it's name shares an origin with turban", "Liliaceous plant with a spring flower".)