Riotous spree in which the bar is overturned (5)
I believe the answer is:
revel
'riotous spree' is the definition.
'revel' can be an answer for 'spree' (I've seen this before). I'm not sure about the 'riotous' bit.
'the bar is overturned' is the wordplay.
'the bar' becomes 'lever' (lever is a kind of bar).
'is overturned' says the letters should be written backwards.
'lever' written backwards gives 'REVEL'.
'in which' acts as a link.
Can you help me to learn more?
(Other definitions for revel that I've seen before include "Make merry, have a ball" , "Paint the town red" , "Take great pleasure" , "Lever (anag.)" , "Celebrate with a lever, strangely" .)