It's unchanged when put up to me (4)
I believe the answer is:
same
'it's unchanged' is the definition.
('same' can be similar in meaning to 'unchanged')
'when put up to me' is the wordplay.
'when' becomes 'as'.
'put up' shows that the letters should be reversed in order.
'as' back-to-front is 'sa'.
'sa'+'me'='SAME'
(Other definitions for same that I've seen before include "Identical or similar" , "uniform" , "Aforesaid" , "Identical, unchanged" , "Equal in amount or value" .)