Stunning barrel inside (3)
I believe the answer is:
tun
'stunning barrel inside' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'stunning barrel inside' is the wordplay.
'inside' says the answer is hidden in the clue.
'TUN' is hidden within 'stunning barrel'.
Can you help me to learn more?
(Other definitions for tun that I've seen before include "Large cask for liquid" , "vessel" , "beer barrel" , "Large cask for wine or beer" , "Large cask (holding 252 gallons)" .)