Again make a sap reduce expenses (8)
I believe the answer is:
retrench
'reduce expenses' is the definition.
(I've seen this before)
'again make a sap' is the wordplay.
'again' becomes 're' (prefix meaning 'again').
'make a sap' becomes 'trench' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
're'+'trench'='RETRENCH'
Can you help me to learn more?
(Other definitions for retrench that I've seen before include "Cut back, tighten one's belt" , "Make economies" , "Curtail" , "Cut back expenses" , "Reduce spending in hard times" .)