Angry if rule is broken (6)
I believe the answer is:
ireful
'angry' is the definition.
('ireful' can be similar in meaning to 'angry')
'if rule is broken' is the wordplay.
'is broken' indicates anagramming the letters.
'if'+'rule'='ifrule'
'ifrule' anagrammed gives 'IREFUL'.
(Other definitions for ireful that I've seen before include "mad" , "Angry" , "very cross" , "Showing resentment" , "Full of wrath" .)