One lambasted for keeping old cut off (8)
I believe the answer is:
isolated
'cut off' is the definition.
(I've seen this before)
'one lambasted for keeping old' is the wordplay.
'one' becomes 'i' (Roman numeral).
'lambasted' becomes 'slated' (I am not sure about this - if you are sure you should believe this answer much more).
'for keeping' is an insertion indicator.
'old' becomes 'o' (abbreviation as in OT - Old Testament).
'slated' going around 'o' is 'solated'.
'i'+'solated'='ISOLATED'
Can you help me to learn more?
(Other definitions for isolated that I've seen before include "kept separate" , "Set apart from others" , "Alone, set apart" , "Remote; lonely" , "Segregated" .)