Every now and then, coloured part of puzzle (4)
I believe the answer is:
clue
'part of puzzle' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'every now and then coloured' is the wordplay.
'every now and then' means one should take alternating letters (letters selected at regular intervals).
The alternate letters of 'coloured' are 'CLUE'.
Can you help me to learn more?
(Other definitions for clue that I've seen before include "crossword guide" , "Hint to help the solver" , "Indication, hint" , "Aid to detection" , "Hint, tip" .)