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 can't see how they can define each other.
'of turning back initially' is the wordplay.
'turning' shows that the letters should be reversed in order.
'initially' suggests taking the first letters.
The first letter of 'back' is 'b'.
'of' reversed gives '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" .)