Bucket's light, reportedly (4)
I believe the answer is:
pail
'bucket's' is the definition.
('pail' can be a synonym of 'bucket')
'light reportedly' is the wordplay.
'light' becomes 'pale' ('pale' can be similar in meaning to 'light').
'reportedly' shows a homophone (sound like).
'pale' is a homophone of 'PAIL'.
(Other definitions for pail that I've seen before include "A bucket as for water" , "Container; sounds like dim" , "it may go down well" , "Cylindrical vessel" , "water-carrier" .)