Ruby present sent back in amazement (6)
I believe the answer is:
wonder
'amazement' is the definition.
(I know that wonder is a type of amazement)
'ruby present sent back' is the wordplay.
'ruby' becomes 'red' (synonyms).
'present' becomes 'now' (both can mean the current period).
'sent back' is a reversal indicator.
'red'+'now'='rednow'
'rednow' in reverse letter order is 'WONDER'.
'in' is the link.
(Other definitions for wonder that I've seen before include "Feeling of surprise and admiration" , "Feel doubt; awe" , "Ponder" , "Transmitted; despatched" , "amazement" .)