A plot, brief, extraordinarily remunerative (10)
I believe the answer is:
profitable
'remunerative' is the definition.
(similar in meaning)
'a plot brief extraordinarily' is the wordplay.
'extraordinarily' indicates anagramming the letters.
'a'+'plot'+'brief'='aplotbrief'
'aplotbrief' is an anagram of 'PROFITABLE'.
(Other definitions for profitable that I've seen before include "useful" , "Rewarding" , "Money-spinning" , "Cost-effective" , "offering good returns" .)