Ditch soldiers, at first, to make savings (8)
I believe the answer is:
retrench
'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 "Economise, cut back" , "Cut back, tighten one's belt" , "Make economies" , "Reduce, say expenditure or operations" , "Reduce expenses" .)