Wild revel in the bar (5)
I believe the answer is:
lever
'the bar' is the definition.
(lever is a kind of bar)
'wild revel' is the wordplay.
'wild' indicates an anagram.
'revel' is an anagram of 'LEVER'.
'in' is the link.
(Other definitions for lever that I've seen before include "Exert pressure" , "Rod" , "Revel (anag.)" , "Pivoting bar, handle" , "Bar turning on a fulcrum" .)