It's amazing to see gigantic bird soaring (3)
I believe the answer is:
cor
'it's amazing' is the definition.
(both are expressions of surprise)
'gigantic bird soaring' is the wordplay.
'gigantic bird' becomes 'roc' (I've seen this before).
'soaring' shows that the letters should be reversed in order (in a down clue, letters 'soar' up).
'roc' written backwards gives 'COR'.
'to see' is the link.
(Other definitions for cor that I've seen before include "Blimey" , "Expression of surprise" , "Gosh" , "Surprised expression" .)