A supporter of turning back initially (3)
I believe the answer is:
fob
'a supporter' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'of turning back initially' is the wordplay.
'turning' says the letters should be written in reverse.
'initially' suggests taking the first letters.
The initial letter of 'back' is 'b'.
'of' backwards is 'fo'.
'fo'+'b'='FOB'
Can you help me to learn more?
(Other definitions for fob that I've seen before include "Small watch pocket" , "Waistcoat pocket" , "Kind of watch carried in pocket" , "Ornament worn on a watch-chain" , "Chain attached to watch" .)