Little devil messed up Dee’s hamper (6)
I believe the answer is:
impede
'hamper' is the definition.
(I know that hamper can be written as impede)
'little devil messed up dee's' is the wordplay.
'little devil' becomes 'imp' (an imp is a little demon).
'messed up' is an anagram indicator.
'dee' anagrammed gives 'ede'.
'imp'+'ede'='IMPEDE'
(Other definitions for impede that I've seen before include "Hold back" , "Delay or obstruct" , "Obstruct or thwart" , "Hinder, be obstructive" , "Hinder, inhibit" .)