Observe trace of repetition in most of new version (6)
I believe the answer is:
remark
'observe' is the definition.
(I know that observe can be written as remark)
'trace of repetition in most of new version' is the wordplay.
'trace of' suggests taking the first letters.
'in' is an insertion indicator.
'most of' means to remove the last letter.
'new version' becomes 'remake' (I've seen this in another clue).
The initial letter of 'repetition' is 'r'.
'remake' with its last letter taken away is 'remak'.
'r' placed within 'remak' is 'REMARK'.
(Other definitions for remark that I've seen before include "Make mention of" , "Incidental observation" , "what someone says?" , "Observation - notice" , "Written or spoken comment" .)