A hairdo, say, to wear down (6)
I believe the answer is:
abrade
'wear down' is the definition.
(I've seen this in another clue)
'a hairdo say' is the wordplay.
'hairdo' becomes 'braid' (braid is a kind of hairdo).
'say' shows a homophone (sound like).
'braid' sounds like 'brade'.
'a'+'brade'='ABRADE'
'to' is the link.
(Other definitions for abrade that I've seen before include "Wear away by friction" , "Scratch" , "Scrape away, erode" , "Shave" , "Rub off or scrape away" .)