Bird and ruler fuming (7)
I believe the answer is:
reeking
'fuming' is the definition.
('reek' can be a synonym of 'fume')
'bird and ruler' is the wordplay.
'bird' becomes 'ree' (I've seen this in other clues).
'and' says to put letters next to each other.
'ruler' becomes 'king' (king is a kind of ruler).
'ree'+'king'='REEKING'
(Other definitions for reeking that I've seen before include "Emitting smoke" , "Having a foul smell" , "Giving off a strong smell" , "With a very unpleasant smell" , "Stinking" .)