It tempts one to break a rule (4)
I believe the answer is:
lure
'it tempts one' is the definition.
The definition suggests a singular noun which matches the answer.
'break a rule' is the wordplay.
'break' is an anagram indicator.
'rule' with letters rearranged gives 'LURE'.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for lure that I've seen before include "Attraction" , "'Decoy, bait (4)'" , "It's used to attract fish" , "Entice, bait" , "Enticement" .)