Outer garment, note, discarded in Pacific islands (4)
I believe the answer is:
toga
'outer garment' is the definition.
(toga is a kind of outer garment)
'note discarded in pacific islands' is the wordplay.
'note' becomes 'n' (abbreviation).
'discarded in' is a deletion indicator.
'pacific islands' becomes 'tonga' (island nation).
'tonga' with 'n' taken out is 'TOGA'.
(Other definitions for toga that I've seen before include "Roman citizen's robe" , "Roman male garb" , "Roman clothing" , "Robe of ancient Rome" , "Roman tunic" .)