Mary keen somehow to support second lucrative scheme (10)
I believe the answer is:
moneymaker
'lucrative scheme' is the definition.
The definition and answer can be both related to thinking as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'mary keen somehow to support second' is the wordplay.
'somehow' is an anagram indicator.
'to support' is a charade indicator (letters next to each other) (in a down clue, some letters hold up others).
'second' becomes 'mo' (both are short periods of time).
'mary'+'keen'='marykeen'
'marykeen' with letters rearranged gives 'neymaker'.
'neymaker' put after 'mo' is 'MONEYMAKER'.
Can you help me to learn more?
(Other definitions for moneymaker that I've seen before include "Profitable undertaking" , "potential goldmine" .)