Mostly entertain, describing the King (5)

I believe the answer is:

regal

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'mostly entertain describing the king' is the definition.
I can't tell whether this defines the answer.

'mostly entertain' is the wordplay.
'mostly' means to remove the last letter (most but not all of the word).
'entertain' becomes 'regale' (I've seen this before).
'regale' with its final letter removed is 'REGAL'.

Can you help me to learn more?

(Other definitions for regal that I've seen before include "Royal - 5 down (anag)" , "Kingly glare?" , "Fit for a monarch" , "befitting a king" , "Befitting a monarch" .)

I've seen this clue in The Independent.

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