Vessel in which a nut gets cracked (3)
I believe the answer is:
tun
'vessel' is the definition.
(type of vessel for beer)
'a nut gets cracked' is the wordplay.
'gets cracked' is an anagram indicator.
'nut' is an anagram of 'TUN'.
'in which' is the link.
(Other definitions for tun that I've seen before include "Container of beer" , "Large cask for wine or beer" , "Nut found in large cask" , "vessel" , "beer barrel" .)