Extremely rude chap, one with interim authority (6)
I believe the answer is:
regent
'one with interim authority' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe you can see a link between them that I don't see?
'extremely rude chap' is the wordplay.
'extremely' means to remove the middle letters (only the extremes of the word are used).
'chap' becomes 'gent' (I've seen this in other clues).
'rude' with its middle removed is 're'.
're'+'gent'='REGENT'
Can you help me to learn more?
(Other definitions for regent that I've seen before include "Closely; almost" , "acting chief" , "Person who rules for a sovereign" , "One acting for monarch who is a minor" , "Stand-in ruler" .)