Flower garland that is left to be sent back (3)
I believe the answer is:
lei
'flower garland' is the definition.
(I've seen this in another clue)
'that is left to be sent back' is the wordplay.
'that is' becomes 'ie' (abbreviation for id est, 'that is' in Latin).
'left' becomes 'l' (common abbreviation).
'to be sent back' is a reversal indicator.
'ie'+'l'='iel'
'iel' back-to-front is 'LEI'.
(Other definitions for lei that I've seen before include "show of affection?" , "Flower arrangements" , "Flower garland of Hawaii" , "Hawaiin flower garland" , "Blooming string" .)