For a start, concocted a lulu of a plan! (9)
I believe the answer is:
stratagem
'for' is the definition.
Both the answer and definition are singular nouns.
Perhaps you can see an association between them that I don't see?
'a start concocted a lulu of a plan' is the wordplay.
'concocted' indicates anagramming the letters.
'lulu of a plan' becomes 'gem' (I am not sure about this - if you are sure you should believe this answer much more).
'start' with letters rearranged gives 'strat'.
'strat'+'a'+'gem'='STRATAGEM'
Can you help me to learn more?
(Other definitions for stratagem that I've seen before include "Artifice" , "could be a trick" , "A cunning plan or scheme" , "Start game with cunning plan" , "Device" .)