Ditch soldiers, at first, to make savings (8)
I believe the answer is:
Here is my best explanation:
'to make savings' is the definition.
'ditch soldiers at first' is the wordplay.
'ditch' becomes 'trench' (trench is a kind of ditch**).
'soldiers' becomes 're' (Royal Engineers).
'at first' says to put letters next to each other.
'trench' after 're' is 'RETRENCH'.
(Other definitions for retrench that I've seen before include "Reduce expenses", "To make economies", "live more economically", "Cut down expenditure", "Conserve or cut down", "Shorten", "Cut back, tighten one's belt", "Cut back spending", "Make economies" and "Cut down to economise".)