Stylish harbour in the Seychelles (6)
I believe the answer is:
sporty
'stylish' is the definition.
(I've seen this in another clue)
'harbour in the seychelles' is the wordplay.
'harbour' becomes 'port' (I've seen this before).
'in the' means one lot of letters goes inside another.
'seychelles' becomes 'SY' (international car registration for the Seychelles).
'port' placed within 'sy' is 'SPORTY'.
(Other definitions for sporty that I've seen before include "preferring to play" , "Athletic" , "(Of car) with rapid acceleration" , "Energetic" , "Like athletes" .)