Tailor is fool to hurry back of blazer (8)
I believe the answer is:
Here is my best explanation:
'tailor' is the definition.
'fool to hurry back of blazer' is the subsidiary indication.
'fool' becomes 'clot' (I've seen this in other clues).
'to hurry' becomes 'hie' ('hie' can be a synonym of 'hurry').
'back of' suggests the final letters.
The final letter of 'blazer' is 'r'.
'is' is the link.
(Other definitions for clothier that I've seen before include "Supplier of things to wear", "Shopkeeper", "One selling material or garments", "tailor", "trader", "Person who sells garments", "Outfitter", "Draper", "who has particular habits?" and "Merchant who sells men's suits etc".)