Murphy is possibly apt to duck (6)
I believe the answer is:
potato
'murphy' is the definition.
(synonyms)
'possibly apt to duck' is the wordplay.
'possibly' is an anagram indicator.
'duck' becomes 'o' (resembles zero - 'duck' in cricket).
'apt'+'to'='aptto'
'aptto' is an anagram of 'potat'.
'potat'+'o'='POTATO'
'is' is the link.
(Other definitions for potato that I've seen before include "Root vegetable" , "Murphy (informal)" , "Vegetable with eyes" , "E.g. King Edward" , "Spud (6)" .)