Simpleton, possibly old one (6)
I believe the answer is:
noodle
'simpleton' is the definition.
(I've seen this before)
'possibly old one' is the wordplay.
'possibly' is an anagram indicator.
'old'+'one'='oldone'
'oldone' is an anagram of 'NOODLE'.
(Other definitions for noodle that I've seen before include "Staple of Chinese cuisine" , "Foolish person or slangy head" , "Simpleton - strip of pasta" , "Form of pasta" , "Goose" .)