I get new gains in marks (8)
I believe the answer is:
insignia
'marks' is the definition.
(I've seen this before)
'i get new gains in' is the wordplay.
'get new' indicates anagramming the letters (get a new order of the letters).
'gains'+'in'='gainsin'
'gainsin' is an anagram of 'nsignia'.
'i'+'nsignia'='INSIGNIA'
(Other definitions for insignia that I've seen before include "Emblems of rank" , "Badge or emblems of office" , "Distinguishing emblem or badge" , "Badge worn to show official position" , "Stars and stripes, say" .)