Rule can become related to fission (7)

I believe the answer is:

nuclear

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'fission' is the definition.
(synonyms)

'rule can become' is the wordplay.
'become' indicates anagramming the letters.
'rule'+'can'='rulecan'
'rulecan' is an anagram of 'NUCLEAR'.

'related to' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.

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(Other definitions for nuclear that I've seen before include "type of power supply" , "Type of energy" , "Concerning subatomic particles" , "Such power available" , "Involving part of an atom" .)

I've seen this clue in the Sydney Morning Herald.

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