Colourless bucket, say (4)
I believe the answer is:
pale
'colourless' is the definition.
(similar in meaning)
'bucket say' is the wordplay.
'bucket' becomes 'pail' (synonyms).
'say' indicates a 'sounds like' (homophone) clue.
'pail' sounds like 'PALE'.
(Other definitions for pale that I've seen before include "Stake, lacking colour" , "stick" , "A bit of fencing" , "heraldic stripe" , "Without much colour" .)