Something in garden, a big one, cultivated (7)
I believe the answer is:
begonia
'something in garden' is the definition.
I can't judge whether this definition defines the answer.
'a big one cultivated' is the wordplay.
'cultivated' is an anagram indicator.
'a'+'big'+'one'='abigone'
'abigone' is an anagram of 'BEGONIA'.
Can you help me to learn more?
(Other definitions for begonia that I've seen before include "bloomer" , "colourful flower" , "Herbaceous plant whose flowers have no petals" , "Common garden plant" , "Tropical plant" .)