Garland that is left to be put up (3)
I believe the answer is:
lei
'garland' is the definition.
(I know that garland can be written as lei)
'that is left to be put up' is the wordplay.
'that is' becomes 'ie' (abbreviation for id est, 'that is' in Latin).
'left' becomes 'l' (common abbreviation).
'to be put up' shows that the letters should be reversed in order.
'ie'+'l'='iel'
'iel' in reverse letter order is 'LEI'.
(Other definitions for lei that I've seen before include "ready in Romania" , "Garland of flowers in Hawaii" , "Garland of flowers, may accompany 5 Down" , "What Romanians spend" , "Floral necklace" .)