Severely criticise ruler getting upset about nothing (5)
I believe the answer is:
roast
'severely criticise' is the definition.
(I've seen this before)
'ruler getting upset about nothing' is the wordplay.
'ruler' becomes 'r' (abbreviation for regina, e.g. in ER ).
'getting upset' says the letters should be written backwards.
'about' becomes 'tsa' (I can't explain this - if you can you should believe this answer much more).
'nothing' becomes 'O' (looks like zero - 0).
'tsa'+'o'='tsao'
'tsao' in reverse letter order is 'oast'.
'r'+'oast'='ROAST'
Can you help me to learn more?
(Other definitions for roast that I've seen before include "Oven-cooked joint" , "Cook (meat) in oven" , "Traditional Sunday joint?" , "Carpet" , "Feel hot" .)