The large one with the elastic (5)
I believe the answer is:
lithe
'elastic' is the definition.
(I've seen this before)
'the large one with the' is the wordplay.
'the large' becomes 'l'.
'one' becomes 'i' (roman numeral).
'with' says to put letters next to each other.
'l'+'i'+'the'='LITHE'
(Other definitions for lithe that I've seen before include "Of body, flexible and supple" , "showing great athletic ability" , "Elastic" , "Supple and graceful" , "able to move supply" .)