In financial terms, a bit of trouble (6)
I believe the answer is:
rouble
'in' is the definition.
The answer and definition can be both quantities as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'financial terms a bit of trouble' is the wordplay.
I cannot really see how this works, but
'bit' could be 'o' (resembles 0, a binary digit or bit) and 'o' is found in the answer.
'trouble' could be 'rub' (I've seen this before) and 'rub' is present in the leftover letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for rouble that I've seen before include "Russian coin" , "Foreign money" , "Currency of 13" , "Monetary unit of Russia" , "Unit of money in Russia" .)