Dash of colour in spun yarn produces striking effect (5)
I believe the answer is:
eclat
'striking effect' is the definition.
(I've seen this before)
'dash of colour in spun yarn' is the wordplay.
'dash of' says to take the initial letters (a small amount of the word).
'in' is an insertion indicator.
'spun' says the letters should be written in reverse.
'yarn' becomes 'tale' (synonyms).
The initial letter of 'colour' is 'c'.
'tale' written backwards gives 'elat'.
'c' inserted within 'elat' is 'ECLAT'.
'produces' is the link.
(Other definitions for eclat that I've seen before include "Social distinction in France" , "Fame -- style" , "Acclaim; showy display" , "Brilliance" , "Universal approval" .)