A little thing requiring some danger money (4)
I believe the answer is:
germ
'a little thing' is the definition.
The answer and definition can be both related to thinking as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'some danger money' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'GERM' is hidden in the letters of 'danger money'.
'requiring' acts as a link.
Can you help me to learn more?
(Other definitions for germ that I've seen before include "Cause of some diseases" , "Microbe, bacterium" , "Start of an idea" , "Micro-organism causing illness" , "starting point" .)