Shows amazement, back inside Japanese pagoda (5)
I believe the answer is:
gapes
'shows amazement' is the definition.
(I've seen this in another clue)
'back inside japanese pagoda' is the wordplay.
'back' is a reversal indicator.
'inside' indicates the answer is hidden within the clue.
'sepag' is hidden within 'japanese pagoda'.
'sepag' back-to-front is 'GAPES'.
(Other definitions for gapes that I've seen before include "Looks on with open mouth" , "goggles" , "Opens mouth wide in surprise" , "Looks amazedly into pages" , "Yawns" .)