Fastidious neckwear will show refinements (8)
I believe the answer is:
niceties
'show refinements' is the definition.
'niceties' can be an answer for 'refinements' ('nicety' can be a synonym of 'refinement'). I am not certain of the 'show' bit.
'fastidious neckwear' is the wordplay.
'fastidious' becomes 'nice' (similar in meaning).
'neckwear' becomes 'ties' (I've seen this in another clue).
'nice'+'ties'='NICETIES'
'will' acts as a link.
Can you help me to learn more?
(Other definitions for niceties that I've seen before include "delicacies" , "Shades" , "refinement" , "Degrees of precision" , "Fine points" .)