A smart cravat or tie, primarily (5)
I believe the answer is:
ascot
This clue might be a double definition.
'a smart cravat' is the first definition.
'ascot' can be an answer for 'cravat' (ascot is a kind of cravat). I am not sure about the 'a smart' bit.
'tie primarily' is the second definition.
'Ascot' can be an answer for 'tie' (Ascot is a type of tie). I'm unsure of the 'primarily' bit.
'or' is the link.
Can you help me to learn more?
(Other definitions for ascot that I've seen before include "Where the Queen often sees racehorses" , "Fungus affecting wood" , "prestigious meeting" , "Town with racecourse" , "English course" .)