Bulb lit up after adjustment (5)
I believe the answer is:
tulip
'bulb' is the definition.
(I've seen this before)
'lit up after adjustment' is the wordplay.
'after adjustment' indicates an anagram.
'lit'+'up'='litup'
'litup' anagrammed gives 'TULIP'.
(Other definitions for tulip that I've seen before include "Plant at the centre of the Dutch financial bubble of 1637" , "Dutch export" , "Spring bulb" , "Flower of the Netherlands" , "Bloomer" .)