Murphy, apt to shoot at Oscar? (6)
I believe the answer is:
potato
'murphy' is the definition.
(synonyms)
'apt to shoot at oscar?' is the wordplay.
'shoot' indicates an anagram (I've seen 'shot' mean this).
'at' is a charade indicator (letters next to each other).
'oscar?' becomes 'O' (phonetic alphabet: alpha, bravo, charlie etc.).
'apt'+'to'='aptto'
'aptto' with letters rearranged gives 'potat'.
'potat'+'o'='POTATO'
(Other definitions for potato that I've seen before include "Vegetable - a hot one is trouble" , "A plant; hole in sock (colloq.)" , "The humble spud" , "Maris Piper?" , "Plant tuber eaten as a vegetable" .)