Walter's wild, being a spendthrift (7)
I believe the answer is:
wastrel
'a spendthrift' is the definition.
(I've seen this before)
'walter's wild' is the wordplay.
'wild' indicates an anagram.
'walters' is an anagram of 'WASTREL'.
'being' is the link.
(Other definitions for wastrel that I've seen before include "Worthless person" , "A useless, good for nothing fellow" , "Spendthrift" , "Profligate" , "Ne'er-do-well" .)