Simpleton finally given reduced earnings on deck (10)

I believe the answer is:

nincompoop

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'simpleton' is the definition.
(nincompoop is a kind of simpleton)

'finally given reduced earnings on deck' is the wordplay.
'finally given reduced earnings' becomes 'nincom' (I am not sure about this - if you are sure you should believe this answer much more).
'on' is a charade indicator (letters next to each other).
'deck' becomes 'poop' (poop deck is a kind of deck).
'nincom'+'poop'='NINCOMPOOP'

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(Other definitions for nincompoop that I've seen before include "Stupid person" , "dunce" , "loony" , "Twit" , "Foolish person" .)

I've seen this clue in The Times.

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