Oddly coloured tip (4)
I believe the answer is:
clue
'tip' is the definition.
(I've seen this in other clues)
'oddly coloured' is the wordplay.
'oddly' means one should take alternating letters (letters in the odd-numbered positions are used).
The alternating letters of 'coloured' are 'CLUE'.
(Other definitions for clue that I've seen before include "Crossword help" , "What's this" , "It helps solve a crime" , "Crossword item" , "Helpful hint" .)