Show popular animal featured in stamp (8)
I believe the answer is:
indicate
'show' is the definition.
('indicate' can be a synonym of 'show')
'popular animal featured in stamp' is the wordplay.
'popular' becomes 'in'.
'animal' becomes 'cat' (I've seen this before**).
'featured in' is an insertion indicator.
'stamp' becomes 'die' (I've seen this in other clues).
'cat' placed inside 'die' is 'dicate'.
'in'+'dicate'='INDICATE'
(Other definitions for indicate that I've seen before include "Point out, make known" , "Point, show, signal" , "(Give a) signal" , "Make a signal" , "Point out, suggest" .)