Partners ask Nike to change leather (9)
I believe the answer is:
snakeskin
'leather' is the definition.
(I've seen this before)
'partners ask nike to change' is the wordplay.
'partners' becomes 'sn' (South and North are partners in the game bridge).
'to change' indicates anagramming the letters.
'ask'+'nike'='asknike'
'asknike' with letters rearranged gives 'akeskin'.
'sn'+'akeskin'='SNAKESKIN'
(Other definitions for snakeskin that I've seen before include "Expensive leather from reptiles" , "that may be cast off" .)