Socialist now sent back - that's a remarkable thing (6)
I believe the answer is:
wonder
'a remarkable thing' is the definition.
The answer and definition can be both related to thinking as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'socialist now sent back' is the wordplay.
'socialist' becomes 'red' (socialism is often associated with the colour red).
'sent back' shows that the letters should be reversed in order.
'red'+'now'='rednow'
'rednow' in reverse letter order is 'WONDER'.
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for wonder that I've seen before include "Ponder" , "Phenomenon - marvel at it" , "Feeling of surprise and admiration" , "Feel doubt; awe" , "Something amazing" .)