More embarrassed, even when upset (6)

I believe the answer is:

redder

I believe this is a double definition.

'more embarrassed' is the first definition.
(someone may go red from embarrassment)

'even when upset' is the second definition.

(Other definitions for redder that I've seen before include "More revolutionary" , "Further to left" , "Blushing more" , "More inflamed" .)

I've seen this clue in The Telegraph.

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