Finally refer to exotic mythical bird (3)
I believe the answer is:
roc
'mythical bird' is the definition.
(I've seen this before)
'finally refer to exotic' is the wordplay.
'finally' suggests the final letters.
The last letters of 'refer to exotic' are 'ROC'.
(Other definitions for roc that I've seen before include "Gigantic bird of Arabian legend" , "Legendary flier" , "Bird imagined" , "Enormous, mythical bird of prey" , "Mythical bird; sounds like boulder" .)