With inadequate amount done in advance, rep endured rap at work (13)

I believe the answer is:

underprepared

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'with inadequate amount done in advance' is the definition.
I can't tell whether this definition defines the answer.

'rep endured rap at work' is the wordplay.
'at work' indicates an anagram.
'rep'+'endured'+'rap'='rependuredrap'
'rependuredrap' anagrammed gives 'UNDERPREPARED'.

Can you help me to learn more?

(Other definitions for underprepared that I've seen before include "Insufficiently readied" , "Not ready enough for action" .)

I've seen this clue in The Times.

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