Swish clothing provided in catalogue? (8)
I believe the answer is:
classify
'catalogue?' is the definition.
(cataloguing is a kind of classifying)
'swish clothing provided' is the wordplay.
'swish' becomes 'classy' ('classy' can be a synonym of 'swish').
'clothing' means one lot of letters goes inside another.
'provided' becomes 'if'.
'classy' enclosing 'if' is 'CLASSIFY'.
'in' is the link.
(Other definitions for classify that I've seen before include "Arrange in categories" , "Sort by category" , "Arrange in divisions" , "Make secret for security reasons" , "catalogue?" .)