"They're worth money," the twit put in (6)
I believe the answer is:
assets
'they're worth money' is the definition.
The definition suggests an adverb but the answer is not.
'twit put in' is the wordplay.
'twit' becomes 'ass' (I've seen this in another clue).
'put' becomes 'set' (both can mean to place or position).
'in' indicates putting letters inside.
'ass' placed around 'set' is 'ASSETS'.
'the' acts as a link.
Can you help me to learn more?
(Other definitions for assets that I've seen before include "Property owned by person or business" , "Advantages" , "worldly goods" , "Useful skills" , "Total value of possessions" .)