Problem finding Russian cash behind central heating (7)
I believe the answer is:
trouble
'problem' is the definition.
(I know that problem can be written as trouble)
'russian cash behind central heating' is the wordplay.
'russian cash' becomes 'rouble'.
'behind' says to put letters next to each other.
'central' says to take the centre.
The central letter of 'heating' is 't'.
'rouble' after 't' is 'TROUBLE'.
'finding' acts as a link.
(Other definitions for trouble that I've seen before include "Disquiet" , "Effort - (cause of) worry" , "'Care, distress (7)'" , "Disturb; unpleasantness" , "Hot water (if you are in it!)" .)