One tucking into acorn nuts and a sweet potato (7)
I believe the answer is:
ocarina
'sweet potato' is the definition.
(synonyms)
'one tucking into acorn nuts and a' is the wordplay.
'one' becomes 'i' (Roman numeral).
'tucking into' means one lot of letters goes inside another.
'nuts' is an anagram indicator (nuts can mean crazy).
'and' means one lot of letters go next to another.
'acorn' with letters rearranged gives 'ocarn'.
'i' going inside 'ocarn' is 'ocarin'.
'ocarin'+'a'='OCARINA'
(Other definitions for ocarina that I've seen before include "Primitive wind instrument" , "music-maker" , "Simple wind instrument" , "Terracotta wind instrument" , "Egg-shaped wind instrument with finger holes" .)