Overdraft arranged reflected experimental environment (4,3)
I believe the answer is:
test-bed
'experimental environment' is the definition.
(environment where tests or experiments can be done)
'overdraft arranged reflected' is the wordplay.
'overdraft' becomes 'debt' (I am not sure about this - if you are sure you should believe this answer much more).
'arranged' becomes 'set' (similar in meaning).
'reflected' shows that the letters should be reversed in order (letters reflected back).
'debt'+'set'='debtset'
'debtset' backwards is 'TEST-BED'.
Can you help me to learn more?
(Other definitions for test-bed that I've seen before include "Experimental rig" , "Trial piece of equipment" , "Trials installation" , "Trial installation" .)