Shilling cut, save (5)
I believe the answer is:
spare
'save' is the definition.
('spare' can be a synonym of 'save')
'shilling cut' is the wordplay.
'shilling' becomes 's'.
'cut' becomes 'pare' (I've seen this before).
's'+'pare'='SPARE'
(Other definitions for spare that I've seen before include "A feature of trousers" , "Free" , "Lean and treat mercifully" , "Extra item just in case" , "Let off; extra" .)