Strip of colour runs right through a fillet (6)
I believe the answer is:
streak
'strip of colour' is the definition.
'streak' can be an answer for 'strip' (thesaurus). I am not certain of the 'of colour' bit.
'runs right through a fillet' is the wordplay.
'right' indicates one should take the final letters (the letter on the right of the word).
'through' is an insertion indicator.
'fillet' becomes 'trek' (I can't explain this - if you can you should believe this answer much more).
The final letter of 'runs' is 's'.
'a' put within 'trek' is 'treak'.
's'+'treak'='STREAK'
Can you help me to learn more?
(Other definitions for streak that I've seen before include "Part of Ukraine" , "Stripe of contrasting colour" , "Go faster" , "Move very fast; thin strip" , "Move very quickly" .)