Ambiguous rule can get broken (7)
I believe the answer is:
unclear
'ambiguous' is the definition.
(similar in meaning)
'rule can get broken' is the wordplay.
'get broken' indicates an anagram.
'rule'+'can'='rulecan'
'rulecan' anagrammed gives 'UNCLEAR'.
(Other definitions for unclear that I've seen before include "Doubtful" , "Cloudy or opaque" , "Ill-defined or not easily understood" , "Not apparent" , "Indistinct" .)