Reigning without backup is awful! (9)

I believe the answer is:

repugnant

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'awful' is the definition.
(thesaurus)

'reigning without backup' is the wordplay.
'reigning' becomes 'regnant' (synonyms).
'without' is an insertion indicator ('without' can be similar in meaning to 'outside').
'backup' becomes 'pu' (I am not sure about this - if you are sure you should believe this answer much more).
'regnant' placed around 'pu' is 'REPUGNANT'.

'is' acts as a link.

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(Other definitions for repugnant that I've seen before include "Abhorrent" , "vile" , "Very unwelcome" , "Offensive to the mind" , "Extremely distasteful" .)

I've seen this clue in The Daily Express.

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