Channel Island one discarding king's dress (4)
I believe the answer is:
sari
'dress' is the definition.
(I know that sari is a dress)
'channel island one discarding king's' is the wordplay.
'channel island' becomes 'Sark' (Sark is one of the Channel Islands).
'one' becomes 'i' (Roman numeral).
'discarding' is a deletion indicator.
'king' becomes 'K' (abbreviation for king in chess).
'sark'+'i'='sarki'
'sarki' with 'k' removed is 'SARI'.
(Other definitions for sari that I've seen before include "Hindu woman's dress" , "South Asian garment (variant spelling)" , "Traditional Indian garment" , "Asian dress" , "Eastern garment" .)